没有评论家的支持，库兹涅茨的曲线就无法幸免。 实际上，库兹涅茨本人在他的论文中还强调了“他的数据的脆弱性”。 评论家对库兹涅茨假说及其图形表示的主要观点是基于库兹涅茨数据集所使用的国家。 批评人士说，库兹涅茨曲线并不反映单个国家经济发展的平均进程，而是代表了数据集中国家之间经济发展的历史差异和不平等现象。 数据集中使用的中等收入国家被用作这一主张的证据，因为库兹涅茨人主要使用拉丁美洲的国家，与类似国家的经济发展相比，这些国家的经济不平等水平一直很高。
Without the support of critics, Kuznets’s curve cannot be spared. In fact, Kuznets himself emphasized “the fragility of his data” in his thesis. Critics’ main point of view on the Kuznets hypothesis and its graphical representation is based on the countries used in the Kuznets dataset. Critics say that the Kuznets curve does not reflect the average course of economic development in a single country, but rather represents the historical differences and inequality of economic development among countries in the data set. Middle-income countries used in the data set are used as evidence for this claim, as Kuznets mainly use Latin American countries, which have consistently experienced high levels of economic inequality compared to similar countries.