President Barack Obama and Labor Secretary Thomas Perez. (AP Photo/Pablo Martinez Monsivais))

(CNSNews.com) - The number of Americans who are 16 years or older and who have decided not to participate in the nation's labor force has climbed to a record 90,609,000 in September, according to data released today by the Bureau of Labor Statistics.

The BLS counts a person as participating in the labor force if they are 16 years or older and either have a job or have actively sought a job in the last four weeks. A person is not participating in the labor force if they are 16 or older and have not sought a job in the last four weeks.

In from July to August, according to BLS, Americans not participating in the labor force climbed from 89,957,000 to 90,473,000, pushing past 90,000,000 for the first time, with a one month increase of 516,000.

In September, it climbed again to 90,609,000, an increase of 136,000 during the month.

In January 2009, when President Barack Obama took office, there were 80,507,000 Americans not in the labor force. Thus, the number of Americans not in the labor force has increased by 10,102,000 during Obama's presidency.

The labor force participation rate, which is the percentage of the non-institutionalized population 16 years or older who either have a job or actively sought one in the last four weeks, was 63.2 percent in September. That was unchanged from August.

When President Obama took office in January 2009, the labor force participation rate was 65.7 percent.

The percentage of the civilian non-institutionalized population over 16 that was employed also remained constant from August to September at 58.6 percent. When President Obama took office in January 2009, the employment-population ratio was 60.6 percent.

The overall national unemployment rate--which is the percentage of people participating in the labor force who actively sought a job and did not find one in September--was 7.2 percent. That was a slight drop from the 7.3 percent unemployment rate in August. When President Obama took office in 2009, the unemployment rate was 7.8 percent.

The number of people actually employed increased by 133,000 last month, climbing from 144,170,000 in August to 144,303,000 in September. When Obama took office in January 2009, there were 142,153,000 Americans employed--meaning the number has increased by 2,150,000 over the past 57 months.

One reason for the increasing number of people not in the labor force is the aging of the Baby Boom generation, whose members have begun retiring--and are not being replaced by an equal number of young people entering the labor force.

Another reason is that female participation in the labor force has been declining. In January 2009, the female labor force participation rate was 59.4 percent. In September 2013, it was 57.1 percent.