The sharp decline in Chinese stocks is approaching a milestone: With a 4% drop Friday, the market has fallen by nearly half since its peak last fall. The decline has wiped out nearly $2.5 trillion of wealth and is testing the government's apparent resolve to let the market find equilibrium on its own.

The plunge has slashed the savings of millions of Chinese investors who jumped into the market as it rose six-fold in two years. It is crimping expansion in the country's nascent financial sector and may put a squeeze in corporate...