The PISA 2018 results showed that students of Beijing, Shanghai, Jiangsu and Zhejiang topped the rankings in reading, mathematics and science and China's school children are now the smartest in the world. OECD secretary-general Angel Gurria said the students from the 4 Chinese provinces had "outperformed by a large margin their peers from all of the other 78 participating countries" and the 10% most socio-economically disadvantaged students in these 4 areas "also showed better reading skills than those of the average student in OECD countries, as well as skills similar to the 10% most advantaged students in some of OECD countries". He cautioned that these 4 provinces and municipalities "are far from representing China as a whole." Yet their combined populations amount to over 180 million people, and the size of each region is equivalent to a typical OECD country even if their income is well below the OECD average.  "What makes their achievement even more remarkable is that the level of income of these four Chinese regions is well below the OECD average".