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.

The markets moved higher today, with most economists predicting minimal damage from a short-term government shutdown -- a GDP impact of between 0.1% and 0.2% for a one-week shutdown, and 0.3% for two weeks. As the closing bell rang, the Dow Jones Industrial Average (DJINDICES:^DJI) had moved 62 points, or 0.41%, higher, while the S&P 500 rose 0.8% and the Nasdaq was up 1.23%.

A few Dow winners
American Express (NYSE:AXP) and Visa (NYSE:V) saw their respective shares rise by 0.54% and 1.11% today, after the companies announced that they, along with MasterCard, were proposing a safer way to make digital payments. The new idea is to use a "token" system that would add an additional layer of security and eliminate the need for merchants, digital wallets, and others to store account numbers. Credit card fraud losses for banks continue to increase each year, with the most recent data indicating that losses in 2012 rose from 5.07 cents per $100 in volume to 5.22 cents.  

Shares of Merck (NYSE:MRK) ended the day as the Dow's biggest winner, gaining 2.38% after announcing that it will eliminate 8,500 of its 81,000 jobs as part of a plan to cut $2.5 billion in expenses. The full savings are expected to be realized by 2015, as the company expects to spend $2.5 billion to $3 billion during restructuring.

And finally, on the day the Affordable Care Act's insurance exchanges opened for business, shares of UnitedHealth Group (NYSE:UNH) rose. The price move comes despite a number of issues and glitches occurring this morning with a number of the exchanges throughout the country. Some states found their servers overloaded by the influx of customers accessing their websites. But despite the problems, both now and in the days leading up to today, and even given the reluctance of some big insurers to jump into every state exchange, investors bid shares higher today. UnitedHealth rose 1.35%.

Fool contributor Matt Thalman has no position in any stocks mentioned. 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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