London - The turmoil on Chinese share and currency markets, and worries about the true extent of the country’s economic slowdown continue to rattle investors. The health of the Chinese economy is crucial for metals and minerals prices. China represents more than 70% of the seaborne trade in iron ore and imports roughly 40% – 50% of the world’s base metal production. But getting a handle on China’s real GDP numbers is difficult with Beijing showing a propensity to massage official numbers to fit its agenda and assuage any doubters about its ability to steer the economy. So far Chinese authorities have maintained the country remains on track to meet official forecasts of 7% GDP growth in 2015. That would be the slowest in more than two decades but still a healthy clip for an economy that’s now the world’s biggest in terms of purchasing power.