Why Bank of America, JPMorgan, Wells Fargo Are Finally Waking Up

C Chart C data by YCharts

NEW YORK (TheStreet) -- Citigroup  (C) , Bank of America  (BAC) and JPMorgan Chase  (JPM) are finally showing signs of life.

The three largest U.S. banks have lagged the S&P 500  since late-2009 when this current bull market took hold. But that's beginning to change. Bank stock over the past four weeks are showing strength, prompted in part by U.S. Treasury yields that have begun to rebound.

Keep in mind that ten-year Treasury yields hit 2.34% on Aug. 15, their lowest level since, June 19 2013. And though they touched that level again on Aug. 28, they've risen during September to 2.61%.

Meanwhile, the S&P 500 is up less than 1% over the past month, whereas Citigroup shares are up 3.4% and Bank of America shares have added 5.2%. JPMorgan Chase has gained 3.10% and shares of Wells Fargo  (WFC) , the fourth U.S. banking giant and the only one that has managed to outperform the broader market since it bottomed in early 2009, are up 4.4% since Treasury yields made their recent move.

The fuel for this move, of course, has been treasury yields.

Higher interest rates benefit banks because it improves their net interest margins-the difference between what it costs them to borrow money and what they can charge for a loan. Banks do particularly well longer term rates rise faster than short term rates, but even a parallel move in rates would benefit the big banks, argues Chris Mutascio, analyst at Keefe, Bruyette and Woods.

Bank stocks have done especially well since Wednesday's Fed meeting, when some investors appeared to interpret interest rate projections released by the Federal Reserve as a sign that short-term rates would rise faster than previously anticipated. Mutascio argues that those projections say very little, since they include the forecasts of Fed officials who don't vote on interest rates and show a wide range.

"It's ahead of the fundamentals a little bit because the rate rise may not occur til mid-next year," Mutascio said. "You won't really get the benefit of that fully until mid-2016 and maybe even 2017 but it is a catalyst nonetheless that people are going to point to in terms of buying the bank stocks, especially because they've underperformed year to date."

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Disclosure: TheStreet's editorial policy prohibits staff editors, reporters and analysts from holding positions in any individual stocks.

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