Where to find the latest statistics of brain drain in the world? Where to find the latest statistics of brain drain in the world?

I would appreciate your suggestions.
Well this is not easy to answer because there is no single measure of brain drain.

For example, many times brain drain is just measured as net immigration from a country (since it is reasonable to assume, and also supported by evidence, that its the smarter and more entrepreneurial people who leave). If you want to measure it by just immigration you could use the UN migration stock data.

Of course, the above approach is very crude. There are other approaches that look migration by education levels. These usually use census data that you can find for every particular country at their statistical office web page. There is also interesting dataset on this commissioned by European Commission, see here, but it only covers OECD countries and its recorded only in 5-year intervals. 

There are also some 'fancy' ways how brain circulation can be measured such as by tracking author affiliations, like in this report, but I am not aware of any dataset on this that would be consistently kept up to date. However, nowadays many journals require authors to make their dataset public so you can just search in google scholar the recent articles on this and make data request to journal.