More than 60 percent of gaokao champions in the past 60 years, especially those who studied science, went abroad after earning their bachelor's degree, with many never returning, indicating a serious brain drain among top scorers.

Experts said the phenomenon resulted from many reasons and factors.

"For example, some did not come back because of the climate or food security problems," said Zhao Deguo, chief editor of the website cuaa.net and a compiler of the report.