They promised to spare no effort to free more than one billion of their fellow men, women and children from extreme poverty, and to make the right to development a reality for all.
And they set themselves precise benchmarks by which their success in keeping these promises could be measured, in the year 2015.
Those benchmarks have come to be known as the Millennium Development Goals, or MDGs. First among them is the pledge to reduce by half the proportion of people in the world living on an income of less than one dollar a day. Others include the pledge to halt, and begin to reverse, the spread of HIV/AIDS; and the pledge to integrate the principles of sustainable development into every country's policies and programmes, so that our children and grandchildren will not face the threat of living on a planet irredeemably spoilt by human activities, or whose resources are not sufficient for their needs.
Will the world reach these goals by 2015? It depends, in great part, on China.
Your population is so large, and your economy is growing so rapidly, that your impact on all global statistics is enormous. It is theoretically possible that we might succeed in halving the proportion of very poor people in the world by 2015, simply because China had succeeded in lifting almost all its people out of that category, even if most countries in Africa still had the same proportion.