China's Shanghai Composite fell approximately 43% from its June 2015 peak to its August 2015 low during the stock-market crash.
The index reached 5,178.19 on June 12, 2015, after a rapid rise driven partly by retail investor participation and margin borrowing. It then dropped sharply, reaching 2,927.29 on August 26. The fall erased a large portion of the preceding rally and prompted authorities to introduce measures intended to support prices and stabilize trading.
The turbulence reflected concerns about excessive valuations, leveraged investors, slowing economic growth, and forced selling. It also affected international markets because China had become central to global growth expectations.
The 2015 episode is sometimes blended with China's later 2016 circuit-breaker turmoil. Those were related periods of market stress, but the approximate 43% peak-to-trough decline refers to the 2015 Shanghai Composite sell-off.