中国是5%的净流出

查了一下全部的排名

http://www.gallup.com/poll/124193/potential-net-migration-change-developed-nations.aspx

下面解释了抽样方法

Results are based on aggregated telephone and face-to-face interviews with 259,542 adults, aged 15 and older, in 135 countries from 2007 to 2009. The 135 countries surveyed represent 93% of the world's adult population. In Gulf Cooperation Council countries, only Arab nationals and Arab expatriates were surveyed. Index values have been rounded to the nearest integer value ending in a 0 or 5.

For most countries, aggregated sample sizes (across three years of surveys) range between 1,000 and 3,000 interviews. One can say with 95% confidence that the country-level margin of sampling error, accounting for weighting and sample design, ranges from ±3 percentage points to ±6 percentage points. Results are projected to the total population of each country aged 15 and older, using 2008 World Bank population estimates.