Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

On the last day of August, a month which has not been good for investors, the major indexes look as if they will close lower for both the session and the past 30 days. As of 12:45 p.m. EDT the Dow Jones Industrial Average (DJINDICES:^DJI) is down 0.29% for the day and 5% for the month. The S&P 500 (SNPINDEX:^GSPC) is down 0.3% today and 4% for the month, while the Nasdaq is down 0.72% today and 1.5% for the month.

One of those reasons for today's market dip is the slight drop in consumer sentiment. The University of Michigan Consumer Sentiment Index read 85.1 in July, and in August the figure slipped to 82.1. July's result was the highest level we had seen in nearly six years, so the small pullback from that high shouldn't be much of a concern. And given that economists had been expecting a reading of 80 for August, the result is a nice surprise. But at the end of the day, sentiment is lower than it was last month, and that's never good. 

Big losers on the Dow
Shares of both Microsoft (NASDAQ:MSFT) and Hewlett-Packard (NYSE:HPQ) are down about 1% each today, and the lower consumer sentiment report may be among the culprits. As kids head back to school, whether it be college or high school, these days they all need computers. Given low confidence in the economy and especially wage growth, parents are likely hesitant to pay up for a new laptop or PC, opting instead to let their children use older models.

Also, a report came out yesterday from the IDC stating that emerging markets -- an area in which PC growth was still happening -- are now slowing down. The IDC said tablets are hurting PC demand in these markets, just as they have in more developed areas of the world. In the past, China and India helped offset declines in PC sales in the U.S. and Europe, but that will no longer be the case. 

Shares of UnitedHealth (NYSE:UNH) are down 0.9% today after news broke yesterday that Aetna, another health insurer, had pulled out of another health insurance exchange. Part of the ObamaCare health plan is that the insurance companies will be part of an exchange, which is supposed to help offer the lowest prices for insurance. But as the day when ObamaCare is set to take effect draws near, and as more exchanges are set up, it seems more apparent that the insurance companies do not like what they see. While it will take time to tell whether the companies can make money through these exchanges, some investors don't seem to want to wait around. 

Fool contributor Matt Thalman owns shares of Microsoft. Check back Monday through Friday as Matt explains what caused the Dow's winners and losers of the day, and every Saturday for a weekly recap. Follow Matt on Twitter @mthalman5513

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