Financials are taking it on the chin so far today, led by Citigroup (C 2.82%), which is looking particularly anemic with a 0.28% drop less than one hour before noon. Except for JPMorgan Chase (JPM 1.44%), which is up 0.05%, big banks are glowing red: Bank of America (BAC 1.70%) is down 0.06%, and Wells Fargo has dipped 0.23% since the opening bell this morning.

What's going on? One big upset occurred earlier today when it was reported that manufacturing may have taken a hit this month, as evidenced by the Chicago PMI business barometer index falling to 49 -- the lowest in three and a half years.

As economic data goes, this isn't great, and both the Dow and S&P 500 (^GSPC 1.20%) are showing the strain today, as well. Despite the dampening effect of this report on the banking sector, it goes to show how sensitive these stocks are to this type of information, absent any particular negative news about the industry as a whole.

For Citi, however, there is one other tidbit that might explain why it is down a smidgen lower than its peers. The bank is currently in negotiations with airlines US Airways Group and the parent company of American Airlines, AMR Corp., concerning whether Citi or Barclay's (NYSE: BCS) will provide the credit card business to the newly merged airline. Despite the fact that Citi has serviced American for 26 years, the outcome of the negotiations is still up in the air -- and it could be making investors queasy.

On the other hand, analysts have noted that a rise in home prices will provide a lift to Citi and Bank of America, and today's positive Case-Shiller Home Price Index report might be responsible for the slight uptick in Citi's share price that I've seen over the past half hour. After all, bad news travels fast -- but sometimes, good news travels faster.

With a successful annual meeting under its belt, Citi's future is looking better than ever, so it's important to keep in mind that it is the overall performance of a stock that really counts. As Foolish, long-term investors, we recognize the fact that one-day changes in share price don't make or break an investment. Even stocks have good days and bad days, so it's important to realize that sometimes they're not portents of dire news, but merely squiggles that we can safely ignore.