The US economy isn't accelerating much going into year-end, at least based on December's PMI flashes. The manufacturing index is down a sizable 1.2 points so far this month to 48.2, convincingly below breakeven 50 to indicate month-over-month contraction in the sector's composite activity. In an offset, services rose a half point to 51.3 which, however flat (close to breakeven 50), is still the best score since July.

The key reading in both sectors -- new orders -- contracted in manufacturing but expanded in services. Likewise output fell for the manufacturing sample but rose for services. Another key reading -- business confidence -- improved for both sectors but remained below long-run averages. Price readings were mixed with input costs, in part tied to higher wages, rose for both samples while pass through for services slowed but increased for goods.

The PMI flashes are likely to lower forecasts for the ISM manufacturing index, last at 46.7, but perhaps lift those for ISM services, last at 52.7. The results leave Econoday's Relative Performance Index at plus 1 and very near the zero line to indicate that recent US economic data, on net, are hitting Econoday's consensus forecasts.

December's consensus for manufacturing is 49.2 versus 49.4 in November; for services, the consensus is 50.6 versus 50.8.

The flash Composite Purchasing Managers' Index (PMI) provides an early estimate of current private sector output by combining information obtained from surveys of around 1,000 manufacturing and service sector companies. The flash data are released around 10 days ahead of the final report and are typically based upon around 85 percent of the full survey sample. The report tracks changes in variables such as new orders, stock levels, employment and prices across both manufacturing and services. Production is also tracked, defined as"production" for manufacturing and"output" for services. Results are synthesized into a single index which can range between zero and 100. A reading above (below) 50 signals rising (falling) output versus the previous month and the closer to 100 (zero) the faster output is growing (contracting). The report also contains flash estimates of the manufacturing and services PMIs. The data are produced by S&P Global.

Investors need to keep their fingers on the pulse of the economy because it dictates how various types of investments will perform. By tracking economic data such as the purchasing managers' manufacturing indexes, investors will know what the economic backdrop is for the various markets. The stock market likes to see healthy economic growth because that translates to higher corporate profits. The bond market prefers less rapid growth and is extremely sensitive to whether the economy is growing too quickly and causing potential inflationary pressures.