You will be surprised to learn then that it's fallen dramatically. Like in just the last 5 years the perception is completely different, especially among young people.
There are 1.4B Chinese. Like obviously some will want to move away. The question is, per capita, what is the rate of locals fleeing away from each country.
Sure, but this is a statistic Beijing is not even trying to improve: at least during the last 10 years, Beijing sees Westerners as a threat and rarely offers them citizenship or permanent residency.
I doubt people who work in cutting edge areas want to leave, not because of national security but because China is now pumping a lot of money into the areas. Those are the people who are willing to work on a 997 schedule anyway.
And yes there are still a lot of Chinese who do want to go to US, but from other areas.