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.

There are few things investors dislike more than uncertainty. Considering what they do -- buy and sell assets today based on what they believe their value will be in the future -- that makes a lot of sense. So today's uncertainty about the government shutdown undoubtedly caused the anxiety among investors to spill over into the markets, sending them lower. 

When the closing bell rang, the Dow Jones Industrial Average (^DJI -0.11%) was lower by 136 points, or 0.9%, and has now fallen back below the 15,000 mark as it sits at 14,936. The S&P 500 declined 0.85% and the Nasdaq lost 0.98%. Within the Dow, the financials were some of the worst-performing stocks.

Today's bad bunch
Visa (V 0.33%) fell 2.18% and American Express (AXP 0.07%) lost 1.84% while JPMorgan Chase (JPM 0.49%) and Goldman Sachs (GS -0.23%) both dropped by 1.59% and 1.47%, respectively.

Since the government shutdown has put at least 800,000 federal workers on furlough and untold other private-sector workers out of work, there is one obvious reason the financials are taking a hit today: the lack of money flowing through the system. For Visa and American Express, this lack of flowing money may be seen through a lower number of credit card transactions. Since a large number of U.S. workers are not receiving a paycheck, they may be less likely to make purchases outside their basic needs.

In this case, though, the market may be overreacting because, as we saw in 1995 when the government shut down and with the recent vote from Congress, federal employees will likely receive back pay when the shutdown ends.

To me, this would mean that some furloughed workers will use the shutdown as a form of unplanned, forced vacation and not change their spending habits at all. Or since they are off work, they may go shopping to kill time or work around their homes and spend slightly more than they normally would, making this a great buying opportunity for investors looking to build a position in Visa or MasterCard.

As for JPMorgan Chase, today's decline is likely the result of news that it is being charged with manipulating certain credit markets during the London Whale incident. The Commodity Futures Trading Commission notified JPMorgan on September 16 and gave it 14 days to respond to the charges. The bank denied the claims and opted not to settle, which has now set the CFTC and JPMorgan on the path toward a court battle.  

Goldman's drop is harder to explain, although the bank did announce it would bring back Robert Zoellick, who had previously served as vice chairman, international, and left Goldman to be the World Bank Group president, will oversee the advisory board, which helps identify sources of international business or investment for the bank's clients, a position for which he seems eminently qualified.