NEW YORK ( TheStreet) -- Freeport-McMoRan Copper & Gold ( FCX), Southern Copper ( SCCO) and Teck Resources ( TCK) are the metals companies whose shares are likely to suffer the most from a slowdown in China's economy.All three are significant copper producers, and China has been a large copper importer as its economy has grown at a torrid pace. Over the past two years, shares of Freeport-McMoRan, Southern Copper and Teck Resources have shown higher correlations than other metals stocks to the Shanghai Composite stock market index, a barometer of the Chinese economy. Southern Copper has had a 0.83 correlation, which means that when China's stocks move, shares of Southern Copper move in the same direction with 83% regularity. Freeport-McMoRan and Teck have correlations of 0.73 and 0.67, respectively. In comparison, SPDR S&P Metals & Mining ETF ( XME) has a correlation of 0.51 with the Shanghai Composite index. U.S. steel majors U.S. Steel ( X), Nucor ( NUE) and AK Steel ( AKS) have lower correlations of 0.12, 0.42 and 0.29, respectively, as China is a net exporter of steel and does not depend on these companies to feed its manufacturing juggernaut. Recent data point to a slowdown in China's economy, which could pressure these stocks further. China's PMI index dropped to 52.1 in June from 53.9 in May. The next big day for Chinese economic data will be July 15, when Beijing plans to release GDP, CPI and industrial production numbers. Second-quarter GDP likely grew 10.1% according to consensus estimates of analysts polled by Bloomberg. In the first quarter, GDP grew at a significantly faster 11.9%, topping analyst estimates of 11.7%. Shares of Freeport-McMoRan, Southern Copper and Teck already have been under pressure due to China's shrinking copper imports, which account for 27% of global copper demand. Copper imports in May declined 9% month over month and 6% year over year to 396,712 tons. Although this decline indicates a slowing economy, other measures of the Chinese economy -- such as real estate prices -- have continued to grow, which could force Chinese officials to tighten monetary policy, further reducing copper demand.