BOZEMAN, Mont. (AP) — Voting is beginning this week on whether to keep Montana State University's faculty union.

Ballots are being mailed out Wednesday to 400 tenured and tenure-track professors after more than 30 percent of the professors requested a union decertification vote with the state Department of Labor and Industry.

The Associated Faculty of MSU was formed in 1989 by a 12-vote margin, 168 to 156.

The Associated Press reports that professors disagree whether the union has won better pay raises or benefits, caused the faculty to be treated more fairly or resulted in a more democratic campus.

The decertification vote doesn't affect the AFMSU union, which represents about 200 MSU adjunct or non-tenured faculty members.

Ballots must be turned in by April 16.