The U.S. jobless rate was flat at 9.6% in September, but the government’s broader measure of unemployment rose even more to 17.1%, the highest rate since April and down just slightly from the October 2009 high of 17.4%.

The comprehensive gauge of labor underutilization, known as the “U-6” for its data classification by the Labor Department, accounts for people who have stopped looking for work or who can’t find full-time jobs.

The key to the rise in the broader unemployment rate was due to a 612,000 jump in the number of people employed part time but who would prefer full-time work. Meanwhile, the number of discouraged workers and those who classify themselves as “marginally attached” to the labor force also increased.

Those jumps were likely affected by a temporary end to extended unemployment benefits. Earlier this year, Congress let an extension of jobless benefits lapse. During that period people may have dropped out of the work force, and though many returned in August some were still coming back into the system last month.

The 9.6% unemployment rate is calculated based on people who are without jobs, who are available to work and who have actively sought work in the prior four weeks. The “actively looking for work” definition is fairly broad, including people who contacted an employer, employment agency, job center or friends; sent out resumes or filled out applications; or answered or placed ads, among other things. The rate is calculated by dividing that number by the total number of people in the labor force, which was relatively steady this month.

The broader rate increased despite a rise of 140,000 in the number of people who are employed. Meanwhile, the number of unemployed people in the U.S. fell by 93,000. However, the size of the labor force was relatively flat despite population growth, as many people dropped out altogether. That could be the result of long-term unemployed, who have exhausted potentially up to 99 weeks of benefits in parts of the country, giving up on their job searches. The number of people unemployed over 27 weeks fell a bit last month, but still remains high at over 6.1 million. And that figure doesn’t include people who have dropped out of the labor force.

The U-6 figure includes everyone in the official rate plus “marginally attached workers” — those who are neither working nor looking for work, but say they want a job and have looked for work recently; and people who are employed part-time for economic reasons, meaning they want full-time work but took a part-time schedule instead because that’s all they could find.