Purpose

The authors investigate the growth–inequality relationship, using panel data from 13 Southern African Development Community (SADC) countries over the period 1990–2015, to test the validity of the Kuznets and Tribble theories. Furthermore, the authors seek to determine the threshold level at which excessive growth hampers inequality.

Design/methodology/approach

The panel smooth transition regression (PSTR) model has several stages. The authors applied the Lagrange multiplier (LM) test to find the appropriate transition variable amongst all candidate variables, to assess the linearity between economic growth and income inequality and to find the sequence for selecting the order m of the transition function. The authors then estimated the PSTR model, but before facilitating the results, the authors first used the wild cluster bootstrap (WCB)–LM-type test to assess the appropriateness of the selected transition.

Findings

The authors found that at lower growth, income inequality tends to be lower, while if growth increases above US$8,969, inequality tends to increase in the SADC region. The findings combine into a U-shaped relationship, contradicting the Kuznets and Tribble theories.

Originality/value

The contribution of this paper is that it becomes the first to provide the threshold level at which excessive growth increases inequality in the selected countries. This study proposes that policymakers should focus on activities aimed at stimulating growth, in other words, activities such as spending more on infrastructure, drawing up a suitable investment portfolio and spending on technological investment for countries that are below US$8,969. An improvement in these activities will create job opportunities, which in turn will add to economic growth and thus lead to lower income inequality and better social cohesion.

中文翻译：

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经济增长和收入不平等：1990-2015年南共体区域的非线性计量经济学分析

目的

作者利用1990年至2015年期间来自13个南部非洲发展共同体（SADC）国家的面板数据，研究了增长与不平等的关系，以检验Kuznets和Tribble理论的有效性。此外，作者试图确定过度增长阻碍不平等的阈值水平。

设计/方法/方法

面板平滑过渡回归（PSTR）模型有几个阶段。作者应用拉格朗日乘数（LM）检验在所有候选变量中找到合适的过渡变量，以评估经济增长与收入不平等之间的线性关系，并找到选择过渡函数阶数m的顺序。作者随后估计了PSTR模型，但在简化结果之前，作者首先使用了野生簇自举（WCB）-LM型测试来评估所选过渡的适当性。

发现

作者发现，在较低的增长中，收入不平等趋向于降低，而如果增长超过8,969美元，南部非洲发展共同体地区的不平等则趋于加剧。这些发现合并为U形关系，与库兹涅茨理论和Tribble理论相矛盾。

创意/价值

本文的贡献在于，它成为第一个提供阈值水平的机构，在该阈值水平上，过度增长加剧了所选国家的不平等。这项研究建议政策制定者应将重点放在旨在刺激增长的活动上，换句话说，就是要为低于8969美元的国家增加基础设施支出，拟定合适的投资组合和技术投资支出之类的活动。这些活动的改善将创造就业机会，这反过来又将促进经济增长，从而导致收入差距缩小和社会凝聚力提高。