One of the regularly repeated comparisons between the current economic slowdown and the “Great Depression” is that the unemployment rate today, 6.1%, is far less than the 25% (actually 24.9%) unemployment rate in 1933.

The “Great Depression,” of course, is the standard by which economic downturns are measured and usually referred to with capital letters even though it was not the longest economic slump in U.S. history. The Great Depression lasted 43 months -- from April 1929 through March 1933 -- according to the National Bureau of Economic Research, which dates economic cycles. The nation struggled with a 65-month contraction from October 1873 through March 1879, according to NBER.

But what about the unemployment rate? How can we say the 6.1% unemployment in September may be worse than 24.9% in 1933?

One reason is the definition of unemployment and the method used to calculate the unemployment rate.

The Bureau of Labor Statistics, which compiles the unemployment rate from its monthly survey, is precise in defining unemployment in the technical note included in the Employment Situation report:

“People are classified as unemployed if they meet all of the following criteria,” the BLS says. “They had no employment during the reference week; they were available for work at that time; and they made specific efforts to find employment sometime during the four-week period ending with the reference week. Persons laid off from a job and expecting recall need not be looking for work to be counted as unemployed. The unemployment data derived from the household survey in no way depend upon the eligibility for or receipt of unemployment insurance benefits.”

In other words, to be considered unemployed, a person has to be out of work, available for work and actively seeking work. “Unemployed” as an adjective can refer to more people than those collecting unemployment insurance.

According to the most recent BLS report, 9,477,000 people were unemployed, but, according to the Department of Labor, about 3,500,000 people were collecting unemployment insurance under the regular insurance and another 1,432,000 were collecting benefits under the extended program signed into law in June.

That’s far different than the count of unemployed in 1933.

According to a paper prepared in 1948 by Stanley Lebergott, at the time a former official in BLS’s Division of Employment and Occupational Outlook, the number of individuals considered “unemployed” in 1933 ranged from 11,842,000 to 14,728,000, with the BLS count somewhere in between at 12,830.

To compute the unemployment rate, the BLS divides the number of individuals by the total labor force, which consists of those over the age of 16 -- employed and unemployed. The arithmetic applies only to the “civilian non-institutional population” which means it excludes individuals in the armed forces and in prison.

That wasn’t the case in 1933 when the unemployment rate was reported as 24.9%. The definition of the labor force in 1933, according to Lebergott, included individuals in the military and prisoners. It also counted individuals as young as 14.

More significantly, the definition of “unemployed” was not, according to Lebergott, limited to those actively seeking a job.

Several economists suggest that because of those differences, comparing the 24.9% “unemployment rate” of 1933 with the 6.1% rate today might not be appropriate. But the rate today considers only those who want a job. A better comparison, according to John Silvia, chief economist at Wachovia Bank, might be the employment population ratio which measures the number of people with jobs against the entire over-16 population. That ratio, in September, was 62.0% -- which means 38.0% of the over-16 population was not working. Indeed that employment population ratio (or its inverse) more closely matches the 1933 definition.

“Society has changed, so the interpretation of the numbers must also change,” according to Silvia. “The labor market today is very different than in the pre-World War II era. Remember employment is a choice, and many people today are older in retirement and choose not to work. Many teenagers/college students choose not to work in the summers or part-time because their parents are wealthier. Many spouses choose not to work because they can.”

Diane Swonk, chief economist of Mesirow Financial, noted other changes since the “Great Depression.”

“The rate is not comparable for so many reasons,” she said. “The percent discouraged [those not looking for work] is also important, and fewer women were even considered a part of the labor force in 1933 even though they were doing odd jobs to make ends meet.”

Swonk said her “gut guess” was “the true unemployment rate netted even higher than reported in the ‘30s, given the inability to even contact homeless and migrant unemployed, adding, “a major problem in the Depression was that a very large percentage of the labor force relocated from farms to urban areas. We don't have shanty towns yet.”

The employment-population ratio at 62.0% is at its lowest (or, conversely, the percentage of those out work at its highest) since September 2003. The ratio has been as low as 55% -- 45% out of work -- in July 1954, just after a 10-month recession which ended in May of that year.

The unemployment rate may not be the best measure, according to Bill Longbrake, an economist and a Director of First Financial Northwest, but the situation may not be as dire as it was during the Great Depression.

“The 6.1% [published unemployment rate] gives the lowest overall rate, but other more inclusive measures are much higher,” Longbrake said. “We are nowhere near a comparable situation to 1933; however, directionally we are headed in the wrong way and an unemployment rate, as traditionally measured by BLS, is likely heading to the 8% to 9% range during 2009 and perhaps to 10% in 2010, depending upon had badly the global economy fares in coming months.”

Longbrake too said the increased participation of women in the labor force changes the measuring stick.

Maurine Haver, President and CEO of Haver Analytics, dismissed the significance of the change in the minimum age, but added “the more important issue is the definition of who is unemployed.” She added: “The rates today would be somewhat higher if the survey were conducted following the methodology in use in the 1930's.”

That said, Haver rejected the employment ratio, using a similar but different argument than offered by Longbrake.

“Our culture has changed very significantly and we now have all these women workers who would have never considered working in the 1930's.”

So is can we compare the 6.1% unemployment rate today with 24.9% in 1933? The answer, without qualification, is: it depends.