Most low-income students who have top test scores and grades do not even apply to the nation's best colleges, according to a new analysis of every high school student who took the SAT in a recent year.The pattern contributes to widening economic inequality and low levels of mobility in this country, economists say, because college graduates earn so much more on average than nongraduates do. Low-income students who excel in high school often do not graduate from the less selective colleges they attend.Only 34 percent of high-achieving high school seniors in the bottom fourth of income distribution attended one of the country's 238 most selective colleges, according to the analysis, conducted by Caroline M. Hoxby of Stanford and Christopher Avery of Harvard, two longtime education researchers. Among top students in the highest-income quartile, the figure was 78 percent.Staying localThe findings underscore that elite public and private colleges, despite a stated desire to recruit an economically diverse group of students, have largely failed to do so.Many top low-income students instead attend community colleges or four-year colleges closer to their homes, the study found. The students often are unaware of the amount of financial aid available or simply do not consider a top college because they have never met someone who attended one, according to the study's authors, other experts and high school guidance counselors."A lot of low-income and middle-income students have the inclination to stay local, at known colleges, which is understandable when you think about it," said George Moran, a guidance counselor at Central Magnet High School in Bridgeport, Conn. "They didn't have any other examples, any models -- who's ever heard of Bowdoin College?"Whatever the reasons, the choice frequently has major consequences. The colleges that most low-income students attend have fewer resources and lower graduation rates than selective colleges, and many students who attend a local college do not graduate. Those who do graduate can miss out on the career opportunities that top colleges offer.The study is beginning to receive attention from scholars and college officials because it is more comprehensive than other research on college choices. It suggests that the problems, and the opportunities, for low-income students are greater than previously thought."It's pretty close to unimpeachable -- they're drawing on a national sample," said Tom Parker, the dean of admissions at Amherst College, which has aggressively recruited poor and middle-class students in recent years. That so many high-achieving, lower-income students exist "is a very important realization," Parker said, and he suggested that colleges should become more creative in persuading them to apply.Top low-income students in the nation's 15 largest metropolitan areas do often apply to selective colleges, according to the study for the high school class of 2008. But such students from smaller metropolitan areas -- like Bridgeport; Memphis; Sacramento, Calif.; Toledo, Ohio; and Tulsa -- and rural areas typically do not.