Mrs Bani Gupta of Calcutta became depressed when her husband died. But she decided to join a women's association, and slowly emerged from her depression. "So many women came with such serious problems that my own crisis seemed insignificant," she says. She's just one of nearly 600 million people aged 60 and over in the world today, and India has more than any other country. The numbers have grown for good reasons - because of medical advances and improvements in nutrition which have led to longer life expectancy, even in poor countries. By 2020, there will be over 1 billion people over 60, and 2 billion by 2050. And most of them will be in the developing world, where the numbers of the elderly will rise rapidly from 171 million in 1998 to 1,594 million in 2050.