Each of the Big Four banks took a pounding last week, but none quite as hard as Citigroup (NYSE:C), and this week isn't shaping up to be much better. Down 2.56% about two and a half hours into trading, the superbank sheered off 5.82% last week, for a grand total loss-to-date of 8.36%. There's little question what's driving these losses, so the real question is, when will they stop, or at the very least, slow down?

It's been a hard day's week
To recap, last Wednesday Federal Reserve Chairman Ben Bernanke announced that the central bank's program of monthly bond purchases might start to be tapered off beginning later this year: if, and he made it clear it is a very big if, encouraging economic data continues to comes in.

But all investors heard was that quantitative easing was going away, and markets around the world tumbled. Here in the U.S., the S&P 500 is down 4.11% from Wednesday's close. The Dow Jones Industrial Average is down 3.71% for the same time period.

Foolish bottom line
In terms of Citi itself, it's a slow news period. Sometimes no news is good news, and that's the case right now. Meanwhile Bank of America (NYSE:BAC) investors are forced to bite their nails as they await the outcome of a trial over soured mortgages sold by the bank's Countrywide Financial unit, which could cost the bank tens of billions of dollars. In that sense, it's good to be a Citi investor right now.

But in terms of this market sell-off, don't look for it to end too soon. In addition to other objectives, Bernanke may have been hoping to let the air out of a potential bubble in the stock market, driven by four years of excess liquidity supplied by the Fed through its quantitative easing programs. There's a strong case to be made for a bubble: With all the market highs we've seen over the last six months, what has that been based on? Great economic data? There's been none of that. There's been encouraging economic data, but not great economic data.

But the good news here is, Citi is a fundamentally strong company. It's come a thousand miles since the depths of the financial crisis. Leadership is strong and steady in the form of CEO Michael Corbat. And the bank is well positioned to tap into emerging market growth. And while said markets may be down right now, developing markets are only to keep developing, and the world is only going to get more and more connected. Citi is perfectly positioned to take advantage of this growth, much more so than, say, Wells Fargo (NYSE:WFC), who's CEO has stated outright that Wells is a domestically focused bank, and happy to stay one.

Stay focused on Citi's fundamentals, Fools, and always remember that you're in the market for the long run. And don't forget to look at this sell-off as a potential buying opportunity, I know I am. Wasn't it Warren Buffet who said when others are fearful, be greedy? 

Fool contributor John Grgurich owns shares of Citigroup. Follow John's dispatches from the not-so-muddy trenches of high-finance and big-banking on Twitter @TMFGrgurich.

The Motley Fool recommends Bank of America and Wells Fargo. The Motley Fool owns shares of Bank of America, Citigroup, and Wells Fargo. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a gripping disclosure policy.