China's stock market mania has reached the dowdy, two-room offices of the Tiancheng pawnshop in central Shanghai. At first sight the trade seems mundane: there are a few dusty cameras in a display cabinet and a middle-aged woman, talking loudly on a mobile phone, is pawning a necklace with a gold-plated heart.

But, unlike pawnshops in most countries, the real business is a steady stream of people putting their homes in hock. "This place is kept alive by people pawning their homes," says Zeng Huiwen, the manager, brandishing the receipt for a Rmb500,000 ($64,000) loan she signed against an apartment.