NEW YORK ( TheStreet) -- The recent short-term rally in copper sent prices to new monthly highs, but the metal is starting to give back some of those gains on news that China has announced plans to make significant reductions in obsolete production capacity into the latter half of the year.China is the world's largest copper consumer, so this development is critical in assessing the long-term outlook for the metal. The announcements this week are being viewed alongside the country's broader economic slowdown, which comes as global supply levels in copper remain healthy and rising. These unfavorable supply and demand conditions suggest a weak road ahead for copper prices, and it is time for those invested in base-metals ETFs such as the iPath Dow Jones UBS Copper Total Return Sub-Index ETN ( JJC) to start reducing exposure. The Chinese economy accounts for roughly 40% of global consumption in refined copper, and early indications of slowing GDP growth have already sent spot prices 12% lower on the year. The preliminary Purchasing Manger's Index (PMI) released earlier in the week came in at 47.7, suggesting Chinese manufacturing activity has fallen to its lowest levels in 11 months. A PMI number less than 50 indicates economic contraction, and the continued weakness seen in these types of surveys suggests that the official GDP targets for the year (now in the range of 7%-7.5%) are starting to look overly optimistic. These trends will only create more challenges for an economy that is already in trouble, as year-on-year growth rates have seen declines in nine of the last 10 quarters.