Dr. Eterno and Dr. Silverman have previously argued that the Police Department’s longstanding focus on reducing major felony crimes has given rise to “a numbers game.”

Their survey is likely to rekindle the debate, which flared up earlier this year after The Village Voice detailed the case of Adrian Schoolcraft, an officer in the 81st Precinct in Brooklyn who secretly gathered evidence, including audio recordings, of crime-report manipulation. Shortly after Mr. Schoolcraft presented the evidence to police investigators, his superiors had him involuntarily committed to a psychiatric hospital, saying he was in the midst of a psychiatric emergency.

The survey, conducted earlier this year, was financed by Molloy College. Dr. Eterno and Dr. Silverman e-mailed a questionnaire to 4,069 former officers who had retired since 1941. Roughly 48 percent — 1,962 retired officers of all ranks — responded.

The respondents ranged from chiefs and inspectors to sergeants and detectives. About 44 percent, or 871, had retired since 2002. More than half of those recent retirees said they had “personal knowledge” of crime-report manipulation, according to the summary, and within that group, more than 80 percent said they knew of three or more instances in which officers or their superiors rewrote a crime report to downgrade the offense or intentionally failed to take a complaint alleging a crime.

The questionnaire did not ask for specific examples, but it did invite respondents to comment. The summary included remarks from six former officers, but did not indicate their ranks.

One officer, who retired in 2005, wrote that he heard a deputy commissioner say in a “pre-CompStat meeting” that a commanding officer “should just consolidate burglaries that occurred in an apartment building and count as one.”

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“Also not to count leap-year stats.”

Another respondent, who retired in 2008, wrote, “Assault becomes harassment, robbery becomes grand larceny, grand larceny becomes petit larceny, burglary becomes criminal trespass.”

Dr. Eterno, now director of the graduate criminal justice program at Molloy College, said he was startled by the responses.

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“What we’ve been able to document here is how many times they’ve seen these manipulations,” he said. “It’s three or more times. That translates, conservatively, into at least 100,000 manipulations, if you extrapolate out the responses to the 35,000 officers on the force.”

Mr. Browne, the police spokesman, dismissed the survey as junk science. He said that the questionnaire was apparently e-mailed to a “tiny sample” of former officers who had retired within the past seven decades, and that Dr. Eterno and Dr. Silverman did not “explain how the respondents differ from the total sample.”

“More importantly, they don’t acknowledge the sampling bias inherent in the self-selection of their respondents,” Mr. Browne said.

Dr. Eterno countered that the survey was sent to officers who had indicated they were willing to return to the force in an emergency, showing that they had a generally positive opinion of the Police Department.

Mr. Browne said the summary’s conclusions drew on respondents’ perceptions, which were not supported by the facts. According to the summary, for example, a majority of respondents indicated that they lacked confidence in the accuracy of the Police Department’s crime statistics, which reflect an 80 percent drop in major crimes since 1990. Many of the retired officers who participated in the survey said they believed crime had declined since 1990, but “not to the extent claimed by N.Y.P.D. management,” the summary said.

Mr. Browne pointed to research conducted by Franklin E. Zimring, a criminologist at Berkeley Law School, that compared the department’s crime data for homicide, robbery, auto theft and burglary to insurance claims, health statistics and victim surveys and found a near-exact correlation.

In an interview Wednesday, Mr. Zimring said his research found that the 80 percent decrease in those four crimes reported by the department from 1990 to 2009 was “real.”

He said that there was always “some underreporting, and there is some downgrading in every police force that I know of,” but that his research showed that any manipulation was too minuscule to significantly affect the department’s crime statistics.