Over the past 25 years, an estimated 240,000 people in Washington state have been arrested for marijuana possession, according to a study by an advocacy group. The study was released as Washington voters are considering a measure on the November ballot to legalize and tax marijuana sales at state-sanctioned stores.

The Marijuana Arrest Research Project is based on data from the FBI, the Associated Press reports. It is a grant-funded group that researches marijuana arrest data for organizations that advocate drug policy reform, the article notes.

Study co-author Harry Levine, a sociologist at Queens College in New York, said that because of the way Washington’s data is reported to the FBI, it is not known how many of the 240,000 were also arrested for other charges. He said based on studies of other states that separate such data, the researchers conclude the overwhelming majority of arrests were for simple misdemeanor possession alone.

The report found that 79 percent of those arrested were age 34 or younger. “And the most serious complication of these arrests is not the night in jail but the criminal record that results,” he told the AP. These arrests can lead to problems renting an apartment or finding a job, he noted.

Most of those arrested were white, but minorities were arrested at a higher rate than whites based on their population.

The number of arrests for marijuana possession rose from 4,000 in 1986, to 11,000 in 2010, the report noted. The researchers estimate that the arrests cost Washington between $200 million and $300 million over the past decade.

The costs of the arrests, and the effects on those who are arrested, are two of the main reasons cited by supporters of the Washington measure, known as Initiative 502. Critics argue the measure would increase teens’ access to marijuana, although it would legalize the drug only for those over 21.

If the Washington measure passes, marijuana would remain illegal under federal law.