中小城市是非洲可持续发展成败的关键

亚瑟 · 敏赛特著

曹康刘梦琳译

Written by Arthur Minsat,

Translated by Cao Kang, Liu Menglin

摘要

非洲城镇化主要发生在中小城市。居民低于 30 万的小城市的增长占到近期城市增长的 58%。这种增长势头会加速，至 2030 年，非洲的城市人口将增加一倍以上，达到8.24 亿人。少于100 万居民的城市对这一增长的贡献将达 77%。

如此大规模的人口聚集可能会影响到非洲可持续发展目标的成败。

城乡之间的强力联系为提高产能和减贫提供了巨大潜力。
如果没有合理的计划，快速城镇化将导致高昂的经济、社会和环境成本。约62% 的非洲城市人口可能已经生活在非正式居民点内。非洲治理空气污染花费了4 470 亿美元，占其 GDP的 1/3，这还是在非洲尚未工业化的情况下。而较小的城市并不具备应对这些挑战的能力，每年在治理污染方面花费不到人均 1 美元。

55 个非洲国家可划分为5 个主要类型来显示非洲大陆的多样性。每个群体中的中阶城市①可以发挥特定作用，以实现可持续发展目标和非洲联盟设定的“2063 年议程”。

① 原文为 intermediary city，指在一个国家的城镇体系中居于主要城市与小镇之间的具有一定规模的城市。此概念主要强调此类城市在城镇体系中的位置和职能，即其“承上启下、中介、中转”的属性，并不必然与城市的绝对人口规模挂钩。经反复考虑，本文采用“中阶城市”的译法，希望学者们批评指正、共同探讨。——编者注

如今，只有约16个非洲国家有国家城镇化战略，且只有不到10个国家了解中阶城市为国家发展所能贡献的潜能。在众多需要采取的行动中，开展有效的多层次治理改革将有助于中阶城市的可持续发展，并实现“可持续发展目标11”。

Abstract:

Africa’s urbanisation is mainly taking place in small and intermediary cities. Cities with less than 300 000 residents captured 58% of recent urban growth. Ongoing trends are accelerating: Africa’s urban population will more than double, reaching 824 million by 2030. Cities with less than 1 million inhabitants will capture 77% of that growth.

Such massive peopling of the continent could make or break the SDGs in Africa:

Strong rural-urban linkages offer big potential to increase productivity and reduce poverty.
Unplanned urbanisation comes at high economic, social and environmental cost. About 62% of Africa’s urban population lives in informal settlements. Air pollution costs Africa USD 447 billion, a third of its GDP. Smaller cities are not equipped to face these challenges: most spend less than USD 1 per resident per year.

Distinguishing five main types among the fifty-five African countries reveals the diversity of the African continent. In each group, intermediary cities can advance the SDGs and the African Union’s Agenda 2063.

Today, only about sixteen African countries have a national urbanisation strategy. Less than ten identify the development potential intermediary cities can offer. Among the many actions needed, reforming multi-level governance will empower intermediary cities to achieve the SDG 11.

关键词 Keywords

非洲城镇化；

工业化；

中阶城市；

可持续发展；

区域发展；

可持续发展目标；

多层次治理；

产业集

African Urbanisation;

Industrialisation;

Intermediary Cities;

Sustainable Development;

Regional Development;

Sustainable Development Goals;

Multi-level Governance; Clusters

引言

非洲城镇化的主要挑战是确保各种规模的城市，尤其是较小的城市，可以作为经济持续转型的催化剂。这是为什么呢？非洲的城市经济增长迅速，但经济转型缓慢。在接下来几十年里，农村地区、城镇和中阶城市仍是非洲经济的重要支柱，并将继续增长。非洲的农村和城市地区都会大大受益于城市和农村经济之间的密切联系，可为非洲即将到来的年轻人兴起创造更多的就业机会。该分析还提出了一种类型学，以探究非洲55个国家的多样性，并理解中阶城市在这些国家可能做出的不同贡献。为了实现其国家目标和可持续发展目标，各国政府会实施新的国家城市战略来掌控中阶城市的可持续发展，并且将主要城市与非洲不断增长的农村经济更好地联系起来。

本文将首先阐述非洲快速城镇化的人口趋势。非洲快速城镇化的特点是农村经济增长支撑下的中阶城市的快速增长，而结构转型进程相对缓慢。发展可持续中阶城市在加速非洲结构转型方面潜力巨大。人们可以发挥农村经济的潜力，向周边地区提供商品和服务，并减轻主要城市的拥挤程度。然而，可持续城市在经济、社会、环境和体制方面也面临着巨大的挑战。为加速非洲的可持续发展，各国政府需要实施发展战略以更好地规划可持续中阶城市的增长。

Introduction

The main challenge of Africa’s urbanisation is to ensure cities of all sizes, particularly the smaller cities, act as catalysers of a sustainable economic transformation.Why? Africa’s urban economies grow fast, but with slow economic transformation. Rural areas, towns and intermediary cities will continue to grow and remain an essential pillar of African economies in the coming decades. African rural and urban areas will strongly benefit from deep linkages between urban and rural economies, which can create many jobs for Africa’s incoming youth bulge. The analysis also proposes a typology to make sense of the diversity of Africa’s 55 countries and understand the different contribution intermediary cities could make in these diverse countries. To realise their national objectives as well as the Sustainable Development Goals (SDGs), governments may carry out new national urban strategies that manage the development of sustainable intermediary cities and better link the primary cities to Africa’s growing rural economy.

This article will set out the demographic trends of Africa’s rapid urbanisation.Africa’s rapid urbanisation is characterised by rapid growth of intermediary cities underpinned by the growing rural economies, with a relatively slow process of structural transformation. Developing sustainable intermediary cities holds great potential for accelerating Africa’s structural transformation. They can develop the potential of rural economies, offer goods and services to the surrounding regions, and relief overcrowded primary cities. However, sustainable cities also face big challenges for their economic, social, environmental, and institutional development. To accelerate Africa’s sustainable development, governments may implement development strategies that better plan the growth of sustainable intermediary cities.

史无前例的非洲人口城镇化趋势

1.1

非洲，一个农村大洲正在迅速城镇化

由 55 个不同国家组成的非洲大陆正在从农村迅速向城市转变。如今，非洲人口中约有 40% 的城市人口。到 2030 年代中叶，非洲大陆大多数地区都将会成为城市地区。预计到2050 年前后，在不断的城镇化进程中城镇化率将达到 56%。尽管城镇化高速推进，但仍有很大一部分非洲人口居住在不断发展的农村地区（图 1）。

非洲现在和未来几十年的发展正在这一趋势下形成。该趋势有两个重要特征：第一，快速城镇化；第二，中阶城市的发展。因为随着非洲社会的城镇化，农村经济也将继续增长。

首先，非洲的城镇化非常迅速。2000—2015 年间增长了 5.9%，世界排名第二，仅次于同期增长了 10.7% 的亚洲。

跟亚洲相似，非洲的城镇化速度是欧洲的两倍。欧洲的城镇化率用了110 年从1800 年的15% 升至1910 年的40%。非洲仅用了其大约一半的时间——60 年，就实现了同样的转变。

非洲城市人口的绝对增长速度更加令人印象深刻。其规模在20年内几乎翻了一番，从1995年的2.37亿增加到了2015 年的4.72亿。预计2015—2035年间会再翻一番。很快，到2020年非洲大陆预计将成为世界上城市居民第二多的地区（5.6 亿），仅次于亚洲（23.48 亿）。相比之下，非洲曾是世界上城市居民人数最少的地区，在1990年只有 1.97亿。

从历史的角度来看，由于非洲和亚洲同时进行着快速城镇化，世界正在见证城市人口的第二次爆炸（图 2）。第一次大的城镇化浪潮发生在1750—1950年间的欧洲、北美、拉丁美洲和加勒比地区。其间，世界城市人口从1500万增加到了4.62亿。当前的城镇化浪潮更大更迅速，预计从现在到2050年这段时间内非洲和亚洲城市中还将增加21亿人。

非洲和亚洲这一新的城镇化浪潮所具有的前所未有的速度和规模，要求其过程更加环保，避免重复以前的错误。例如，与许多经合组织国家一样，中国快速的城镇化和工业化伴随着环境的恶化，与发展和扶贫的收益成正比。尽管中国将赤贫率从1990 年的67% 降至2014 年的 1.4%，但全球20 个污染最严重的城市仍在中国；中国城市周围的河流约有 90% 受到了严重污染（World Bank, 2017; PovcalNet database, World Bank, 2007; Zheng & Khan, 2013）。

同样地，非洲快速城镇化也在付出巨大的环境代价，而且其城市贫困现象比亚洲更普遍。虽然非洲还没有实现工业化（Roy, 2016），但是在2013年因（室外和室内的）空气污染而导致的过早死亡所造成的经济成本约为 4470亿美元，占其GDP的1/3。面对这些新的环境挑战，非洲城市却无法借鉴其他城市的经验。此外，非洲的城镇化发生在一个资源和气候受约束的世界中，将过去城镇化的经验运用到工业化和减少贫困上都是挑战。非洲城市多维贫困指数（MPI）为0.151，是世界次最贫穷地区（AfDB/OECD/UNDP, 2016）南亚的两倍。世界其他地区从未面临过如此重大的环境与发展挑战。

这种大趋势的第二个特点是，非洲的城镇化主要是伴随着中阶城市和城镇的发展而发生的，这也是本文的主题。

The demographic trends of Africa’s urbanisation are unprecedented

1.1

A rural continent, Africa is urbanising rapidly

The African continent, made of 55 diverse countries, is transforming rapidly from rural to urban. The African population is about 40% urban today. By the mid-2030s, Africa will become in majority urban. Around 2050, urbanisation is projected to continue and level off at about 56%. Despite this rapid urbanisation, an important share of the African people will thus continue to reside in growing rural areas (Figure 1).

This mega-trend is shaping Africa’s development now and in the coming decades. It entails two important characteristics:(1) rapid urbanisation and (2) the growth of intermediary cities, because rural economies will continue to grow as African societies are urbanising.

First, Africa’s urbanisation is extremely rapid. It has gained 5.9 percentage points between 2000 and 2015. This is second in the world only to Asia, which gained 10.7 percentage points during the same period.

As Asia, Africa is urbanising twice as fast as did Europe. It took Europe 110 years to move from 15% urban in 1800, to 40% in 1910. Africa has achieved the same transformation in almost half the time: 60 years.

Even more impressive is the rapid growth of Africa’s urban population in absolute terms. The size of Africa’s urban population nearly doubled in 20 years from 237 million in 1995 to 472 million in 2015. Africa’s urban population is expected to almost double again between 2015 and 2035. Soon, in 2020, the African continent is forecasted to have the second highest number of urban dwellers (560 million) in the world after Asia (2 348 million). By contrast, not so long ago, in 1990, Africa was the world’s region with the smallest number of urban dwellers: 197 million.

Looking from a historical perspective, the world is witnessing the second explosion of its urban population due to the simultaneously rapid urbanisation of Africa and Asia(Figure 2). The first major urbanisation wave took place between 1750 and 1950 in Europe, Northern America, and in Latin America and the Caribbean. During that period, the world’s urban population increased from 15 million to almost 462 million. The current wave of urbanisation is bigger and faster. An additional 2.1 billion people are projected to be living in African and Asian cities between today and 2050.

The speed and magnitude of this new urbanisation wave in Africa and Asia calls for a more environment friendly process than in the past, which avoids repeating past mistakes. For instance, in China, as in many OECD countries, rapid urbanisation and industrialisation have come with environmental degradation proportional to the gains in development and poverty reduction. While China has reduced extreme poverty from 67% of the total population in 1990 to 1.4% in 2014, the world’s 20 most polluted cities are located in China; about 90% of China’s rivers around urban areas are seriously polluted (World Bank, 2017), PovcalNet (database), World Bank, 2007; Zheng and Khan, 2013).

Likewise, Africa’s rapid urbanisation is coming at great environmental cost, though urban poverty remains more widespread than in Asia. The estimated economic cost of premature deaths from air pollution (both outdoor and indoor) cost Africa USD 447 billion in 2013, a third of its GDP, although Africa has not industrialised yet (Roy, 2016). As they face those new environmental challenges, African cities cannot borrow from others’ experiences. In addition, Africa’s urbanisation is taking place in a resource and climate-constrained world where it is challenging to repeat past urbanisation experiences to industrialise and decrease poverty. Africa’s urban Multidimensional Poverty Index (MPI) is 0.151, twice the level of South Asia, the next poorest world region (AfDB/OECD/UNDP, 2016). Other world regions have never exhibited such convergence of important environmental and developmental challenges.

The second particularity of this megatrend is that Africa’s urbanisation is mainly taking place through the growth of intermediary cities and towns. This will be the main topic of this article.

1.2

非洲城镇和中阶城市的增长速度超过其首位城市

非洲城镇和中阶城市的发展速度比首要城市和大都市都要快。“2000—2010年，非洲城市增长的58%发生在人口不足30万的城市群中；只有13%的城市群拥有 30 万 ~100万的居民，29%有超过100万的居民。预计2010—2030年，51%的城市增长将发生在小城市群、 16%发生在中阶城市区、33%发生在最大的城市群当中”（AfDB /OECD /UNDP, 2016）。

城镇化主要发生在由农村地区、村庄、城镇和居民少于50 万人的城市组成的连续的城乡结合部当中。超过9.52亿的非洲人——占其人口的82%——居住在这样的城乡结合部中。在不同地区，居住在小于50万居民的定居点的人口比例如下：东非91%、西非 80%、北非77%、中非74%、南非65%。纵观非洲所有城市地区，有55%的地区人口不到50万。

因此，非洲的城镇化在很大程度上以“城市村庄” 的形式出现，城市发展从小村庄扩散到小城镇。所以如今的非洲城乡区别并不是那么明显，农村的生活方式仍然在城镇中普遍存在。伴随着新技术以及更多的移民在农村与城市地区之间传播与移动，城市生活方式也更容易潜移默化地影响农村地区。中阶城市正在成为非洲农村和城市经济之间的网络中的战略节点。

根据世界其他地区的经验（图 3），这意味着其农村人口增长将缓慢下降。除北非国家、南非和小岛屿国家的城镇化经济体外，非洲大部分农村地区的人口会持续增长。非洲城镇化的同时，其农村人口在2045 年以后仍将以年增长率大于 1% 的速度增长。2015— 2050年，预计撒哈拉以南非洲地区将增加超过3.53亿的农村居民，其农村人口的持续增长与世界其他地区形成对比。从全球范围来看，预计农村人口将在2020年之前开始萎缩，而撒哈拉以南非洲地区将是世界农村人口持续增长最多的地区。

尽管城镇化快速进行，但非洲农村地区仍将是其经济发展的基础，城镇化并不能脱离非洲农村地区。把握非洲的城镇化需要透过虚假的“城乡差距”，城市和农村的静态分类不再能够反映变化的城乡关系所具有的混合性质（Agergaard, Fold & Gough, 2010; Berdegurd & Proctor, 2014）。

莫依塞克（Miossec）在突尼斯首次观察到的 “乡村城镇化和城市农村化”现象已成为该大洲城镇化趋势的一个总体特征（AfDB/OECD/UNDP, 2016: 160）。许多村民遵循了更为城镇化的生活方式（部分原因是手机技术的快速普及和城乡之间的循环移民模式）。同时，城市居民继续以前的某些农村活动，特别是为了自身消费而进行的城市农业。大约有40% 的非洲城市居民会“从事某种农业活动” （FAO, 2012）。

1.2

African towns and intermediate cities are growing faster than Africa’s primary cities

African towns and intermediate cities are growing more rapidly than primary cities and metropolises. “Between 2000 and 2010, 58% of Africa’s urban growth happened in urban agglomerations with fewer than 300 000 inhabitants; only 13% in agglomerations with 300 000-1 million inhabitants; and 29% in those with over 1 million inhabitants. Between 2010 and 2030, 51% of the urban growth is forecasted to take place in the small agglomerations; 16% in the intermediate ones; and 33% in the biggest” (AfDB/OECD/UNDP, 2016).

Urbanisation has been happening mostly in towns related to a rural-urban interface defined by a continuum of rural areas, villages, towns and cities of fewer than 500 000 inhabitants. Over 952 million Africans, 82% of Africa’s population, live at such rural-urban interface. Across the different regions, the share of the population living in settlements smaller than 500 000 inhabitants is as follows: 91% in East Africa, 80% in West Africa, 77% in North Africa, 74% in Central Africa and 65% in Southern Africa. Looking at all of Africa’s urban areas, 55% have a population of fewer than 500 000 people.

Africa’s urbanisation has thus to a large extent taken the form of “urban villages”, diffusing urban growth from small villages to smaller towns. As a result, the rural-urban divide is becoming blurred in today’s Africa. Rural lifestyles remain widespread in towns and cities. Urban lifestyles penetrate rural areas more easily, with the diffusion of new communication technologies and increased migration between rural and urban areas. Intermediary cities are becoming strategic nodes in this network between Africa’s rural and urban economies.

An implication is that rural population growth will abate only slowly, in contrast with the experiences of other world regions (Figure 3). Except in the urbanised economies of North African countries, South Africa and the small islands states, most of Africa’s rural areas experienced continued demographic growth. While Africa urbanises, its rural population will continue to grow at a rate of more than 1% per annum beyond 2045. SubSaharan Africa is expected to grow by more than 353 million additional rural dwellers between 2015 and 2050. Continuing rural population growth in most of sub-Saharan Africa contrasts with other world regions. Globally, rural population is forecasted to start shrinking no later than by 2020. Sub-Saharan Africa is the world region where the rural population will continue to grow the most.

Despite rapid urbanisation, Africa’s rural areas will remain essential for economic development. Urbanisation is not disconnected from African rural areas. Understanding Africa’s urbanisation requires going beyond a spurious “rural-urban divide”. Static categories of urban and rural no longer capture the hybrid nature of shifting relations between cities and countryside (Agergaard, Fold and Gough, 2010; Berdegué and Proctor, 2014).

The phenomenon of “urbanisation of the countryside and ruralisation of the cities”, first observed by Miossec in Tunisia, has become a general feature of the continent’s urbanisation trends. (AfDB/ OECD/UNDP 2016: 160). Many villagers have adopted a more urban life-style (in part facilitated by the rapid penetration of mobile phone technology and patterns of circular migration between rural and urban areas). At the same time, urban dwellers continue with some of their previous rural activities, notably urban farming for self-consumption. About 40% of African urban dwellers are “engaged in some sort of agricultural activity” (FAO, 2012).

1.3

非洲快速城镇化尚未导向快速工业化

基于这种情况，非洲中阶城市可以在结构转型中发挥关键作用。在经济学中，结构转型通常被定义为将生产要素在一个部门内部或跨部门重新分配给从事较高生产率的活动。除了这一经济学定义外，结构转型需要：

空间维度，农村工人（如农民）有意迁移到城市，成为制造业或服务业中的蓝领或白领工人。在全球范围内，人均10 000 美元年收入是一个门槛值，高于这一数值该国的城镇化率往往会达到 50%。
人口因素，随着人均收入和城镇化率的提高，生育率趋于下降。

非洲联盟“2063 年议程”将结构转型作为 2063 年非洲领导人实现非洲发展的主要愿景之一。“ 2063 年议程”将结构转型视为一种工业化形式，通过将各个部门的生产要素在农业到制造业和服务业部门之中重新分配来得以实现。中阶城市可以在这一过程中发挥关键作用，为发展当地对农村商品和服务（如农产品）的需求打下基础，并为区域、国家、大陆和全球的市场中的农业、制造业与服务业提供商品与服务。

但是，这种潜力尚未完全发挥，因为在大多数非洲国家中城镇化并未伴随显著的工业化。图4比较了三个区域样本中城镇化与经济转型的速度。11个非洲国家的城镇化速度与11个亚洲国家相当，但是劳动生产率相对缓慢。这一具有挑战性的趋势不止出现在非洲：“ 相比之下，9个拉美国家的城镇化速度更快，但结构转变甚至比非洲国家还慢”（ AfDB/OECD/UNDP 2016: 150）。

这些快速增长的中阶城市可以在加速非洲结构转型中扮演什么样的角色呢？

1.3

Africa’s rapid urbanisation has not yet led to rapid industrialisation

In that context, intermediary cities can play a key role in Africa’s structural transformation. In economics, structural transformation is usually defined as the re-allocation of factors of production to higher productivity activities within a sector or across sectors. Beyond this economic definition, structural transformation entails:

a spatial dimension, in which rural workers (e.g. farmers) tend to move to cities to become blue- or white- collar workers in manufacturing or services. Globally, this can be witnessed through a threshold of USD 10 000 a year per capita, after which countries tend to be 50% urbanised.
a demographic dimension, since fertility ratios tend to decrease with higher income per capita and higher urbanisation rates.

The African Union’s Agenda 2063 envisions structural transformation as one of the main aspirations of African leaders for Africa’s development by 2063.Agenda 2063 tends to mainly perceive structural transformation as a form of industrialisation. This typically happens by re-allocating production factors across sectors, from the farming to the manufacturing and services sectors. Intermediary cities can play a key role in this process, by providing a base to develop local demand for rural goods and services (e.g., farming products) and by providing goods and services in agriculture, manufacturing and services for the regional, national, continental and global markets.

However, this potential is not yet being fully realised because urbanisation is coming without significant industrialisation in most African countries. Figure 4 below compares the paces of urbanisation and economic transformation in three regional samples. The 11 African countries are urbanising at a comparable speed to the 11 countries from Asia. However, labour productivity has been progressing more slowly. This challenging trend is not unique to Africa: “For comparison, the 9 Latin American countries have experienced faster urbanisation but even slower structural change than the African ones” (AfDB/OECD/UNDP 2016: 150).

What role can those rapidly growing intermediary cities play to accelerate Africa’s structural transformation?

中阶城市在非洲结构转型和实现可持续发展目标方面发挥关键作用

中阶城市可以有多个定义，有时会有部分重叠。这些定义基于不同的城市规模和功能标准，通常取决于一个国家的规模。“中阶城市”更倾向于指向城市的功能；而“中等的城市”仅限于表明其规模。

总体而言，非洲中阶城市的门槛往往小于全球门槛（特别是中国的门槛）。在全球范围内，中阶城市人口通常在一个国家最大城市人口的 10%~50% 之间，虽然有些城市的人口可能比这少得多。一般来说，中阶城市可以容纳15万 ~500 万的居民。但是由于单一规模并不适用于所有55个非洲国家，因此本文不会使用固定值来界定中阶城市。非洲人口迅速增长，例如尼日利亚在 2018 年有1.81亿居民，再如塞舌尔这样的小国，其岛屿上只有9.4万居民（UNDESA, 2018）。对55个各具特色的国家使用相同的固定值标准会掩盖非洲的多样性（表 1）。

中阶城市可以理解为在主要城市和城镇之间占据中间位置的城市。从非洲自身背景来看，依据功能比用规模来定义中阶城市更有意义，因为55个非洲国家的城市规模各不相同。除此之外，由于各国往往缺乏数据或不能对数据进行比较，因而无法确定非洲背景下城市及其覆盖区（或腹地）的确切规模。与经合组织国家不同，非洲的数据质量不足以衡量城市能创造多大的集聚经济，因此，根据中阶城市的功能来对其进行定义更为合适。城市功能也是非洲结构转型和实现可持续发展目标的关键问题（表2）。

中阶城市如何使非洲实现结构转型和可持续发展目标？

Intermediary cities can play a key role in Africa’s structural transformation and in achieving the SDGs

Intermediary cities can have multiple, sometimes overlapping, definitions. They are often based on varying criteria of cities’ sizes and functions, which may however depend on the size of a country. “Intermediary cities” tend to refer to cities’ function; “intermediate cities” solely to their size.

In general, thresholds for intermediate cities in Africa tend to be smaller than the global ones (especially the Chinese thresholds).Globally, the population of intermediate cities tends to range between 10-50% of a country’s largest city, although some can be much smaller than these. Usually, intermediate cities tend to host between 150 000 to 5 million inhabitants. Since one size does not fit all 55 African countries, this article will not use fixed thresholds to define intermediary cities. Africa is home to countries with large and rapidly growing populations, such as Nigeria with 181 million inhabitants in 2018, as well as very small countries, such as the Seychelles, which hosts only 94 000 inhabitants across its islands (UNDESA, 2018). Using the same unique thresholds for 55 countries that are so diverse would mask Africa’s diversity (Tablel 1).

Intermediary cities can best be understood as cities that hold an intermediate position between primary cities and towns. In an African context, it makes more sense to define them by their function than by their size, because the 55 African countries have cities of many different sizes. Moreover, data is often lacking or not always comparable across countries to identify the exact size of a city and its catchment area (or hinterland) in the African context. Unlike in OECD countries, data quality is insufficient in Africa to measure to what extent cities can create economies of agglomeration. Hence, it makes more sense to use the function of intermediary cities to define them. It is also the function of cities that matters for Africa’s structural transformation and for realising the SDGs (Table 2).

How can intermediary cities enable Africa to achieve structural transformation and the SDGs?

2.1

中阶城市在国家可持续发展和实现非洲可持续发展目标方面发挥关键作用

简而言之，规划可持续中阶城市和城镇的发展可以在两个主要层级上减轻贫困并促进结构转型，其中一个在城市等级体系的顶端，另一个在该体系低一些的层级：

中阶城市和城镇通过吸纳一部分城市人口增长和农村移民来帮助缓解大城市的拥挤（AfDB/ OECD/UNDP, 2015）。这些城市可以通过更好地行使既有的省级和国家政府职能来提高国家的总体管治能力。中阶城市和城镇可以积极承担作为经济和社会服务中心的角色。
中阶城市可以通过提高生产率和促进周边农村发展，在全国及跨国范围内推广城镇化红利。因此，在国家和跨国经济中，城镇、中阶城市和农村腹地之间的联系非常重要。

有很多非洲中阶城市履行基本经济职能的例子，特别是发展：（1）区域粮食经济；（2）制造业和相关产业；（3）为其腹地提供服务。

首先，中阶城市作为调控农村腹地和大城市之间商品和服务流动的物流点（Haggblade, Hazell & Reardon, 2009），可以帮助缩小城乡差距。在寡头垄断的农业价值链中，批发商和运输商以牺牲农民为代价而获得大额营销利润率，与此同时食品出口商却因缺乏相应储存设施而只能在港口延迟交货，但是中阶城市能够在这种价值链当中建立竞争机制（Rakotoarisoa, Lafrate and & Paschali, 2011: 43）。

西非的粮食经济空前膨胀，主要是因为城镇和中阶城市的发展推动了城镇化进程。1960年以来，西非17个国家饮食变化连同城镇化一起，导致其食品经济出现10倍的膨胀。2010年西非的粮食经济约为1780 亿美元，占地区国内生产总值的36%，超过2/3是在市场上交易（Allen, 2016）。人口增长推动了食品经济膨胀。1950—2010年间西非城市人口增长了22倍（城市居民人数从600万达到1.33亿），这尤其发生在靠近农村地区的小型聚居区当中。西非现在共有1950个其居民超过1万人的聚居区。城市之间的平均距离已经从111 km减少到28km。2000年，94%的高密度农村地区位于至少拥有5万居民的城市覆盖区（OECD, 2013; AfDB/OECD/UNDP, 2016: 159-160）。

中阶城市可以作为农村地区产品的市场以刺激农业生产力。多罗什等人（Dorosh et al, 2012）推算，10万居民到最近的城市去的出行时间从24 小时减少到4小时，会使实际作物产量与潜在作物产量之比增至16倍（图5）。更大规模的农业生产也发展了国家非农部门较低阶段的后农业食品价值链，形成了农业和农村发展的良性循环。

通过中阶城市发展实现的城镇化可以推动农村地区的现代化。城市是农村农业和非农经济的重要市场。在撒哈拉以南非洲，城市地区有助于农村发展：目前城市地区占总人口的40%，食品消费总量（包括家庭生产）的50%和食品市场的60%（Reardon et al, 2013）。较大的城市比城镇消耗更多的食物：为农村地区创造了更大的生产潜力，并且只要物流环节良好，农产品就不需要进口。在西非一个5万居民的城市食品消费量通常达到每年1035万美元，30万居民的城市则达到4480万美元（Yatta, 2006: 149）。中阶城市可加强农村与城市的经济联系，对促进生产力增长至关重要。

其次，中阶城市可以提供必要的集聚经济来发展劳动密集型和成熟的产业，如纺织和农产品加工或类似旅游业这样的服务业，特别是那些不需要高知识溢出的产业。中阶城市可以将一个地区与全球化相连接。

摩洛哥的丹吉尔和非斯、突尼斯的斯法克斯利用其受过良好教育的劳动力和信息通信技术基础设施，成为主要的工业综合体和信息通信技术服务中心。
坦桑尼亚的桑给巴尔市挖掘该地区的文化财富，打造成为了一个国际旅游目的地。

中阶城市可以专门促进成熟产业的发展，引导价值链的升级。一旦大城市的企业掌握了专业化的业务流程就会转向大规模生产，并搬迁到专门从事生产的城市以寻求更低的生产成本（Duranton & Puga, 2004）。

例如

在埃塞俄比亚，新企业进入集群有助于提高该企业对生产相同产品企业的全要素生产率的竞争力，约 0.91%（Siba et al., 2012）。
在坦桑尼亚的阿鲁沙和姆贝亚，同一行业和地区的公司增加10%，会导致其平均成本降低 0.3%~0.4% （Iimi, Humphrey & Melibaeva, 2015）①。一些非洲中阶城市正在发展以贸易和现有非正规经济为基础的制造业。在某些地区（如西非），这些集群最初往往没有中央政府的大力支持。

一些非洲中阶城市正在发展以贸易和现有非正规经济为基础的制造业。在某些地区（如西非），这些集群最初往往没有中央政府的大力支持。

例如

在埃塞俄比亚，国家和地区政府制定了长远的计划在中阶城市打造制造基地，包括在这些城市周边开发经济特区。在哈瓦萨市的周边政府修建了16 km 长、30m 宽的干道。该项目启动之后，哈瓦萨市地块租赁部分的市政收入增加了2.2倍，道路开支增加了6倍（AfDB/OECD/UNDP, 2016），这些对哈瓦萨工业园的建设形成了有益补充。该“绿色工业园区”试点拥有超过40万 m2 的厂房，预计到2018年底可以创造6万个就业岗位和10亿美元的出口额（Hoque, 2017）。
自 1990 年代后期，尼日利亚在拉各斯的 Otigba 集群已经发展成为计算机组装和维修以及计算机零部件制造和销售的次区域中心。
同样，位于尼日利亚东部的内维是拥有75万居民的城市，1980 年代时还是从日本进口汽车备件贸易的交易地，现在已升级为尼日利亚汽车制造基地。如今，尼日利亚70% 的汽车零部件采购来自国内，并且主要来自内维。
在加纳，库马西市拥有“Suame Magazine”，这是一个服务于金属工程和车辆维修的手工作坊集群。多达20万人在那里工作并且学习相关技能，如冶炼废金属、交易汽车零部件、调整卡车发动机和改装电子产品。为了应对集群企业共同面临的挑战，“ Suame Magazine”工业发展组织一直在努力升级培训和本地制造能力。
在摩洛哥，国家和地方政府利用丹吉尔（一个拥有约100 万居民的城市）的地缘战略位置开发了一个经济特区（丹吉尔经济特区），是非洲最大的深海港口之一。经济特区吸引了汽车行业的跨国公司如雷诺和福特在这里进行直接投资，并雇佣了大约6 万名当地员工。它被称为摩洛哥汽车行业的丹吉尔物流中心。
突尼斯在斯法克斯中学建立了一个经济特区，该中心迅速成为该国第二大专门从事信息通信技术的制造中心。
在南非，德班成为汽车零部件制造中心。它在南部非洲发展交流（SADC）以及汽车行业全球价值链（GVCs）中深深融入区域贸易。

第三，中阶城市可以利用规模经济向周边地区提供公共服务。它们可以缓解特大城市的压力。这些大城市的人口估计已超过700 万的预估门槛，在经济合作背景下会造成集聚不经济（这个门槛对于非洲来说较低，因为在非洲经常缺乏公共产品。但是现有的数据也不足以衡量非洲主要和次要城市的“理想”规模是多大）。中阶城市可以作为中心提供卫生服务和教育，并向周边地区传播技术。加大基础设施投资可以减少人们因需要公共服务而进入主要城市的频率。一个更加平衡的城市系统可以减轻公共服务过度延展以及其他因大城市中设施过度集中而造成的负面影响。此外，强化中阶城市有助于在建筑、基础设施和服务（如教育、健康、安全）等非贸易部门创造就业机会，这些部门将随着非洲人口指数的增长而扩大。

中阶城市有助于实现“可持续发展目标1”，即“在世界各地消除一切形式的贫穷”。让人们转移到中阶城市不仅迁移成本较低，相比于诱使工人迁往更远更大的城市而言还能实现更好的减轻贫困的效果。在坦桑尼亚的卡格拉农村地区，1/2的人通过从农业迁移到农村非农经济或中阶城市来摆脱贫困；只有1/7 的人通过移居到大城市而脱贫（Christiaensen & De Weerdt, 2013）。想要实现这一目标，中阶城市有能力为潜在的移民提供足够的公共产品至关重要，这样他们就不会为了找到体面的工作或获得基本的服务而不得不搬到主要城市。然而，目前在许多中阶城市公共产品和服务的水平仍然过低，处于供不应求的状态。

中阶城市为循环迁移和非农就业通勤提供了更多的可能性。发展农村非农就业能够提供额外收入，这样就可以减少农村贫困现象（Owusu, Abdulai & AbdulRahman, 2011）。这样做还可以减轻信贷和流动性限制，使农民能够保存其生产性资产，存有一定积蓄并稳定消费（Barrett, Reardon & Webb，2001）。中阶城市和农村之间的汇款、消费联系以及推动农业工资上涨的压力也有助于农村贫困的减少。

上文分析了中阶城市在非洲结构转型中可以发挥的关键作用，也说明了其功能和作用的不同因经济结构和城镇化水平而异。中阶城市在埃塞俄比亚、摩洛哥和尼日利亚扮演着重要角色，但它们进行的活动也不尽相同。如何理解非洲 55 个国家的多样性和不同的趋势呢？

2.1

Intermediary cities play a key role in sustainable national development and in achieving the SDGs in Africa

In a nutshell, planning the development of sustainable intermediary cities and towns can help alleviate poverty and foster structural transformation by acting at two main levels, one at the top of the urban hierarchy and the other one at the lower part of the urban hierarchy:

Intermediary cities and towns help alleviate the congestion of megacities by capturing a share of urban demographic growth and rural migration (AfDB/OECD/UNDP, 2015). They can enhance the country’s overall governance capacity by better mobilising the available capacity in provincial and national governments. Intermediary cities and towns can assume an active role as economic and social service hubs.
Intermediary cities can spread the benefits of urbanisation nation-wide and across borders by enhancing productivity and promoting development in surrounding rural areas. Connections between towns, intermediary cities and the rural hinterland within the national and transnational economy are therefore critical.

Many examples exist of African intermediary cities that fulfil essential economic functions, notably to develop: (1) the regional food economy, (2) manufacturing and related industries, (3) delivering services to their hinterland.

First, intermediary cities can help bridge the gap between rural and urban areas by serving as logistic points mediating the flow of goods and services between rural hinterlands and larger cities (Haggblade, Hazell and Reardon, 2009). They open up competition in agricultural value chains that are too often oligopolistic: wholesalers and transporters make wide marketing margins at the expense of farmers, while food exporters lack appropriate storage facilities and suffer from delivery delays at ports (Rakotoarisoa, Lafrate and Paschali, 2011: 43).

West Africa has seen an unprecedented expansion of its food economy, largely because of an urbanisation fuelled by the growth of towns and intermediary cities. In 17 West African countries, diet change associated with urbanisation has supported the expansion of the West African food economy tenfold since 1960. West Africa’s food economy is estimated at USD 178 billion for 2010 or 36% of the regional GDP, over two-thirds of which was traded in markets (Allen, 2016). The growth of West Africa’s urban population by a factor of 22 between 1950 and 2010 (from 6 to 133 million urban dwellers) has driven this process, particularly in the smaller agglomerations close to the rural areas. The sub-region now counts 1 950 agglomerations with more than 10 000 inhabitants. The average distance between cities has been reduced from 111 kilometres to 28. In 2000, 94% of high-density rural areas were located in the urban catchment area of towns with at least 50 000 inhabitants (OECD, 2013).”

(AfDB/OECD/UNDP, 2016: 159-160).

Intermediary cities can serve as markets for products from rural areas and stimulate agricultural productivity. Dorosh et al. (2012) estimate that reducing the travel time to the nearest city of 100 000 inhabitants from 24 to 4 hours increases the ratio of actual to potential crop production by 16 times (Figure 5). Greater agricultural production also develops the rural non-farm sector in countries at a lower stage of the post-farm food value chain, creating a virtuous circle of agricultural and rural development.

Urbanisation through the growth of intermediary cities can lead to modernisation in rural areas. Cities are essential markets for rural farm and non-farm economy. In sub-Saharan Africa, the urban sector contributes to rural development: it currently accounts for 40% of the total population, 50% of total food consumption (including home production) and 60% of the food market (Reardon et al., 2013). Larger cities, for instance, consume more food than towns: they offer the potential of more production in the rural areas, provided logistical links work well and agricultural goods are not imported. Food consumption in a West African city of 50 000 inhabitants typically reaches USD 10.35 million a year and in a city of 300 000 inhabitants USD 44.8 million (Yatta, 2006: 149). Intermediary cities can strengthen economic linkages between rural and urban areas, which are crucial to enable productivity growth.

Second, intermediary cities can provide the economies of agglomeration necessary to develop labour-intensive and mature industries such as textiles and agro-processing or services like tourism, especially those that do not require high knowledge spill-overs.They can connect a region to globalisation:

Tangier and Fez in Morocco, or Sfax in Tunisia, have leveraged on their educated workforce and ICT infrastructure to become major industrial complex and ICT service centres.
Zanzibar City, Tanzania, has tapped into the region’s cultural wealth to become an international tourist destination.

Intermediary cities can specialise in and foster the development of mature industries, leading to an upgrade in the value chain. Once firms in the big cities have mastered the business processes leading to specialisation, firms switch to mass production and relocate to specialised cities in search of lower production costs (Duranton and Puga, 2004).

For example:

In Ethiopia, entrance of new firms to clusters help gain increase total factor productivity of competing firms producing the same products by 0.91% (Siba et al 2012).
In Arusha and Mbeya (Tanzania), a 10% increase of firms in the same industry and area leads an average of 0.3%~0.4% cost reductions (Iimi, Humphrey and Melibaeva, 2015). ① Several African intermediary cities are developing a manufacturing sector based on trade and the existing informal economy. In certain regions (like West Africa), these clusters often developed initially without much support from central government. For instance, in alphabetical order:
In Ethiopia, the national and regional governments laid out ambitious plans to develop manufacturing bases in the countries’ intermediary cities, including through the development of Special Economic Zones next to intermediary cities. On the urban periphery of Hawassa city, the governments also developed 16 km of 30-metre wide arterial roads. Municipal revenue from plot leasing in Hawassa has increased 2.2-fold since the start of the programme, and spending on roads has increased 6-fold (AfDB/OECD/UNDP, 2016). This complements the construction of the Hawassa Industrial Park. This pilot “green industrial park” boasts over 400 000 m² of factory floor space, and is expected to generate 60 000 jobs and USD 1bn in exports by the end of 2018 (Hoque, 2017).
Since the late 1990s, Nigeria’s Otigba cluster in Lagos has developed into a sub-regional hub for computer assembly and repairs and for the manufacturing and sales of computer parts.
Similarly, Nnewi, a city of 750 000 inhabitants in Eastern Nigeria, upgraded from trading imported Japanese automobile spare parts in 1980s to being the manufacturing base of Nigeria’s automobile sector. Today, 70% of automobile components used in Nigeria are sourced domestically, mostly from Nnewi.
In Ghana, the city of Kumasi houses Suame Magazine, a cluster of artisanal workshops for metal engineering and vehicle repairs. As many as 200 000 people work there with complementary skills such as smelting scrap metal, trading automobile parts, finetuning truck engines, and retrofitting electronics. To support common challenges faced by firms in the cluster, Suame Magazine Industrial Development Organisation has been working to scale up training and local manufacturing.
In Morocco, national and local governments have used the geostrategic location of Tangier (a city of about 1 million inhabitants) to develop a Special Economic Zone (“Zone Économique Spéciale de Tanger”) and one of Africa’s largest deep sea harbours. The SEZ attracts foreign direct investment from multinationals in the automotive sector, such as Renault and Ford, and employs about 60 000 local workers. It is known as the Tangiers logistics hub for automotive industry in Morocco.
Tunisia developed a SEZ in its secondary of Sfax, which has quickly become the country’s second largest manufacturing hub specialised in ICT.
In South Africa, Durban developed as a manufacturing hub for automotive spare parts. It is deeply integrated in inter-regional trade within the Southern African Development Communicty (SADC) as well as into Global Value Chains in the automotive sector (GVCs).

Third, intermediary cities can leverage economies of scale to deliver public services to surrounding areas. They can relieve megacities, which tend to generate diseconomies of agglomeration beyond an estimated threshold of 7 million inhabitants in the OECD context. (This threshold is likely to be lower in African context, where public goods are often lacking. However, the available data is insufficient to measure an “ideal” size of primary and secondary cities in the African context.) Intermediary cities can serve as hubs providing health services and education and disseminating technology to their surrounding areas. Investing in their infrastructure reduces the incidence of people moving to primary cities for public services. A more balanced urban system prevents overstretching public services and other negative effects of over-concentration in large cities. Moreover, strengthening intermediary cities can create jobs in the non-tradable sectors of construction, infrastructure and services (e.g. education, health, security) that will expand with Africa’s exponential demographic growth.

Intermediary cities can help achieve SDG 1 to “end poverty in all its forms everywhere”. Letting people move to intermediary cities may entail lower migration costs and alleviate poverty more efficiently than by enticing workers to move to more distant and larger cities. In rural Kagera, Tanzania, one in two individuals who left poverty did so by transitioning from agriculture into the rural non-farm economy or intermediary cities; only one in seven exited poverty by migrating to a large city (Christiaensen and De Weerdt, 2013). To achieve that objective, it is crucial that intermediary cities can offer sufficient public goods to potential migrants, so that they do not feel compelled to move to primary cities in order to find a decent job or to access basic services. At the moment, however, the offer for public goods and services remains too low in many intermediary cities where the demand outstrips the supply.

Intermediate cities offer more possibilities for circular migration and commuting for off-farm employment. Generating rural off-farm employment can reduce rural poverty by providing additional income (Owusu, Abdulai and Abdul-Rahman, 2011). It can also alleviate credit and liquidity constraints, enabling farmers to preserve their productive assets, generate stocks and stabilise their consumption (Barrett, Reardon and Webb, 2001). Remittances between intermediary cities and rural areas, consumption linkages, and the upward pressure on agricultural wages can also contribute to rural poverty reduction.

Having now analysed the crucial role intermediary cities can play in Africa’s structural transformation, we also see that their functions and roles differ depending on the economic structure and urbanisation levels. Intermediary cities play an important role in Ethiopia, Morocco, and Nigeria, but they do not specialise in the same activities. How can we make sense of Africa’s diversity and of the different trends in Africa’s 55 countries?