The purchases are part of a combined effort by the world's largest growers to revive prices that have fallen more than 60% from a peak in 2011 as trees planted last decade across Asia matured and flooded the market with latex. Demand has also weakened from China, which has set its 2015 economic growth target at 7%, the slowest in 15 years. The country's total rubber imports fell 21% in the first two months of the year