Why is China's stock market in crisis?

Shares have plunged 30% in three weeks, hundreds of firms have suspended dealings and fears that the slump will spill over into other markets are growing

Stock markets in China are tumbling. A three-week plunge has knocked about 30% off Chinese shares since mid-June. China's securities regulator has warned of "panic sentiment" gripping investors, many of whom are individuals that have borrowed heavily to play the stock market.

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