Bank of New York and Northern Trust Corp. are proving more resilient  than other banks to recent stock market swings, because key lines of their   business go full tilt during bull or bear markets.   
The companies act as safekeepers for billions of dollars of securities,  providing bookkeeping, processing, and other services that are necessary   whether people are entering, leaving, or just sitting pat in the market.   
  
The ongoing securities revenues "somewhat insulate these institutions  and allow them to perform better than many traditional bank peers," said   Bradley Ball, banking analyst with Credit Suisse First Boston.   
Indeed, shares of traditional banks that rely primarily on spread income  from gathering deposits and making loans have fallen by one-third from   their summer highs. But Bank of New York and Chicago's Northern Trust,   which offer more than traditional banking services, have dropped less than   15%.       
  
This suggests that at least some banks may be getting what they have  long wanted-assessments based on their diverse business lines, not a   lumping together with shares of all other financial institutions.   
Bank of New York and Northern Trust appear to have broken from the pack.  Though their shares fell 10.31% and 13.1% respectively between July 15 and   Sept. 15, that was far less than the 23.97% plunge in the same period by   the Standard & Poor's bank index, which is made up of a large grouping of   bank stocks.       
"All banks are not equal," said Susan Roth, financial institutions  analyst with Donaldson Lufkin & Jenrette. "Revenue growth prospects, risk   profiles, and competitive positioning vary greatly across the universe."   
  
Bank of New York and Northern Trust even outpace Mellon Bank Corp.,  Pittsburgh, and State Street Corp., Boston, two of the industry's other   securities processing giants.   
Analysts said that's because the market is now drawing a distinction  between institutions such as Mellon, focused largely on adding new   investments, and operations like Bank of New York that cull ongoing income   from an existing body of business.     
Bank of New York "represents the unique combination of a securities  processing powerhouse and a more traditional regional bank," Ms. Roth said. 
With a roughly fifty-fifty split between the traditional and securities  businesses, and a strong emphasis on cost controls, Bank of New York   "justifies a premium valuation," Ms. Roth said.   
  
She sees earnings per-share growth of 10% or more annually based on  management's goals for the next few years. The company wants a 23% return   on equity, a return on assets of 2% or more, and an efficiency ratio of   48%.     
Ms. Roth also likes Northern Trust for "pursuing a strategy that  balances a focus on trust and securities businesses with traditional   lending."   
Northern Trust is heavily into asset management, as are Mellon and State  Street. But Northern Trust targets a more stable group of investors-wealthy   individuals who stay in the market through ups and downs, said Mr. Ball of   Credit Suisse.     
He said both Bank of New York and Northern Trust will probably outpace  peers if the economy goes into an extended downturn. 
"Given their mix of businesses, there should be less slowing on their  revenue growth," Mr. Ball said.