Economist Larry Mishel was troubled by high school graduation statistics that contradicted what he thought was good research. That was particularly true of data used by many politicians and pundits to bemoan a 30 percent dropout rate in American high schools.

"This picture was radically different from what I knew from labor market data I regularly examined in my studies of wage and job trends," said Mishel, president of the Economic Policy Institute, a Washington-based think tank. His research indicated that only about 12 percent of the workforce lacked a high school diploma or its equivalent, so how could the dropout rate be so large?

Political scientist Jay P. Greene also had trouble with the data, but for a different reason. Working as a fellow at the Manhattan Institute and as head of the education reform department at the University of Arkansas, Greene reported that graduation rates seemed to be worse than many people thought, as low as 50 percent in low-income urban neighborhoods.

Experts disagree over who is right, and some say the truth may be somewhere in between. But the dispute has aggravated a widespread feeling that information on how many children are disappearing from public schools is not nearly as accurate as it should be.

"Jay Greene and Larry Mishel have performed the valuable service of exposing the huge inadequacies in the way we measure the percent of students who achieve a regular high school diploma — inadequacies not attended to in over two decades of education reform," said Paul E. Barton, senior associate in the Educational Testing Service's Policy Information Center.

The scholarly strife began with the publication of a book by Mishel and Economic Policy Institute economist Joydeep Roy, "Rethinking High School Graduation Rates and Trends." It takes a big swing at powerful forces, particularly the National Governors Association and its recent report that said high schools are in crisis.

That report, using Greene's data, declared that "about a third of our students are not graduating from high school. About three-fourths of white students graduate from high school, but only half of African-American and Hispanic students do."

Mishel and Roy used U.S. Education Department data that follow student experiences as well as results of Census Bureau household surveys. They got very different numbers: an overall high school graduation rate with a regular diploma of 80 percent to 83 percent, a black student graduation rate of 69 percent to 75 percent and a Hispanic graduation rate of 61 percent to 74 percent.

They say that in the past 40 years, the high school completion rate, including graduates and those passing General Educational Development diploma tests, has gone up substantially and that the black-white gap has shrunk, except in the past 10 years, when there has been little improvement. Only graduation among Hispanics increased during the past 10 years.

Greene and Manhattan Institute research associate Marcus A. Winters say the Mishel-Roy book is too dependent on Education Department studies that follow a representative sample of students over several years and on census surveys that depend on people telling the truth about their success in school. Greene estimates graduation rates by dividing the number of regular diplomas issued by public high schools by an estimate of the number of ninth-graders who entered four years earlier, adjusting for population changes in the interim.

"It may seem that we are talking about just a few percentage points here and there," said John Robert Warren, an associate professor of sociology at the University of Minnesota who agrees with Greene, but "5 percentage points would be 175,000 young people annually."