Postal attrition: How to make statistics say exactly what you want them to

“There are three kinds of lies: lies, damned lies, and statistics.”

On Sunday I mentioned Darrell Issa’s claim that the US Postal Service has an attrition rate of about one percent. I pointed out that the most recent annual numbers showed the postal service losing 3.8% of its career employees in the course of a year. So was Issa just making it up as he went along?

No. Issa was probably using statistics compiled by the Congressional Research Service for its new report, U.S. Postal Service Workforce Size and Employment Categories, 1990-2010, a copy of which appears below. The report accurately states that “USPS’s workforce size has dropped by 171,576 employees (20.3%) in the past 20 years”. Bingo! If the USPS has 20% fewer employees than it had 20 years ago, it has an annual attrition rate of 1%!

Not so fast- latching onto this seemingly obvious number ignores the facts. To start with, in the first half of that time period the USPS, like the US economy, was growing. From 1990 to 2000, the report shows that USPS total complement went from 843,263 to 901,238, an increase of almost 7%! From 2000 to 2010 the USPS began to see declines from electronic diversion, the impact of 9/11, and finally the Great Recession. As volume and revenue plummeted, it stopped hiring and started shedding employees. From 2000 to 2010, total complement went from 901,238 to 671,687, a drop of 25%. Yes, that means you could use the same report to support an attrition rate of either 1% or 2.5%, depending on the time span you select. Look at just the last five years, and the rate is 3.3%. And if you look at just the final two years of that period, the report tells you

“From the end of FY2008 through FY2009, the size of USPS’s workforce declined 7% (53,006 employees), the largest decline in more than 20 years.” and “USPS had 40,395 (6.0%) fewer employees at the end of FY2010 than it did at the end of FY2009”.

So the most recent complete fiscal year numbers reflect an attrition rate of 6%, not 1%. While that number was increased by early out offers, recent attrition still reached 3.8% without significant incentives. Using a 20 year average to estimate attrition is obviously misleading. It’s like telling an investor that the stock market has a reliable 13.4% annual growth rate because the S&P index is 268% higher than it was 20 years ago, even though today’s S&P index is just about where it was in April 1999!.

Beware politicians bearing statistics!

U.S. Postal Service Workforce Size and Employment Categories, 1990-2010

  • DB

    Figures don’t lie, but liars figure.

  • Ugh

    This just proves why you all should keep those math skills polished. 😛

  • OG

    Yet Issa is accusing USPS of using accounting gimmicks when it comes to the massive overfunding(s). Instead of drilling postal management and unions over their negotiated contract, Issa should put his oversight hat on and turn his focus on congress addressing the unfair withholding of postal funds.

    OG

  • Nutzy

    Statistics = garbage in garbage out. Or is that congress?