A former New Zealand prime minister once laughed off emigration of his young compatriots to Australia as an IQ boost for both countries. But a brain drain is no joke. Few developing countries can afford it. It may be argued that China is one that can at this stage of its development because a population of more than 1.3 billion provides a bottomless pool of talent. So the fact that mainland China is the world's biggest source of immigrants may not be cause for alarm - yet. Moreover, the traffic is two-way, with many successful emigrants returning home to seize opportunities created by China's economic rise. Simple figures, however, do not tell the whole story. Mainland China's first report on international migration, issued jointly by the Centre for China and Globalisation and Beijing Institute of Technology law school, is more revealing. More than 150,000 mainlanders obtained overseas citizenship last year, meaning they have made a new home, or an alternative one. The report says the rich and educated elites are becoming the main force in the latest round of emigration, and that many had left in search of a more democratic society, a cleaner environment and better educational opportunities. The main beneficiaries were the US (87,000), Canada and Australia (30,000 each) and New Zealand (6,000). Li Xiaogang, a research director of the Shanghai Academy of Social Sciences, says the elite are leaving because China's social and political development has not kept up with the economic environment in which they achieved their success. They are sending a message to China's leaders that seems reflected in promises by new Communist Party chief Xi Jinping to fight corruption, push reforms begun by late paramount leader Deng Xiaoping, uphold the rule of law and rein in abuses of power. The new wave of migration is a reminder that lifting hundreds of millions from poverty and creating a new middle class also raises expectations. If they are not met, these emigrants may never return.