A new analysis of census records has led a Binghamton University , N.Y., historian to conclude the number of Civil War dead has been underestimated for decades. The usual figure given for the death toll is 620,000. Assistant Associate Professor J. David Hacker has determined the number should be about 750,000.

According to a release by the university, Hacker came up with the new figure by comparing census data instead of going by military records. New data sets produced in the last 10 years allowed him to look at the identity of each person and his or her age, race and birthplace for a census instead of just an aggregate number of people in a certain age group. Hacker realized that civilian deaths were so much lower than soldier deaths, that he could “compare the number of native-born men missing in the 1870 census relative to the number of native-born women missing and produce an estimate from that,” according to the university.

“Hacker looked at the ratio of male survival relative to female survival for each age group,” the university said. “He established a ‘normal’ pattern of survival rates for men and women by looking at the numbers for 1850-1860 and 1870-1880. The he compared the war decade, 1860-1870 relative to the pattern.”

Dean of the Civil War historians, James McPherson, was interviewed by the university for the press release and said he had doubted the 620,000 figure for a long time and the 750,000 conclusion was plausible.

“My guess is that most of the difference between the estimate of 620,000 and Hacker’s higher figure is the result of underreported Confederate deaths,” McPherson told the university.