"Businesses raising money and people buying homes and cars all have faced higher interest rates in recent months as the Fed's campaign to suppress borrowing costs has faltered. The rise in rates reflects optimism that the economy is gaining strength, and an expectation that the Federal Reserve will begin to pull back later this year. But a wide range of financial analysts also see evidence of a Summers effect."Many investors expected that Ms.Yellen would be nominated to replace Ben S. Bernanke as head of the central bank, a choice that would have sent a clear message of continuity. Instead, investors are now trying to anticipate how Mr.Summers might change the Fed."'People don't know what Larry might do,' said Mohamed El-Erian, chief executive of Pimco, the giant bond fund manager. 'There's a lack of a lot of information on Larry's views. We don't have enough information to make an assessment, just some second- and third-hand accounts.'"