Chinese President Hu Jintao says China aims to lift the size of its economy to $4 trillion by 2020 -- effectively quadrupling its gross domestic product of five years ago. A $4 trillion economy would give China's 1.3 billion people a per capita income of $3000 by 2020, compared with about $1230 now. Hu, delivering the keynote address at the Fortune Global Forum in Beijing, said the 2020 target was a "formidable challenge" that would require an uphill battle. But he told the forum China was committed to seizing the window of opportunity to build a prosperous society. CNN quoted Hu as saying that economic development was China's central task and top priority.