translation.en: Spending per student only explains about, well, less than 20 percent of the performance variation among countries, and Luxembourg, for example, the most expensive system, doesn't do particularly well.
translation.zh: 生均教育经费投入 对一个国家教育质量的影响 大约不足20%， 例如，卢森堡是教育投入是最高的， 但其教育效果并不太好。