The Manufacturing Purchasing Managers' Index (PMI) measures the activity level of purchasing managers in the manufacturing sector. A reading above 50 indicates expansion in the sector; below 50 indicates contraction. Traders watch these surveys closely as purchasing managers usually have early access to data about their company’s performance, which can be a leading indicator of overall economic performance. A higher than expected reading should be taken as positive/bullish for the USD while a lower than expected reading should be taken as negative/bearish for the USD.