WASHINGTON — A top White House economist says spending from the $787 billion economic stimulus has already had its biggest impact on economic growth and will likely not contribute to significant expansion next year.Christina Romer, the chair of President Barack Obama's Council of Economic Advisers, said Thursday that the $194 billion already spent gave a jolt to the economy that contributed to growth in the second and third quarters of the year. She told a congressional panel that by the middle of next year, the impact of the stimulus will level off. Romer said spending so far has saved or created 600,000 to 1.5 million jobs but warned that unemployment will remain high, above 9.5 percent, through the end of 2010.
