The claim is floating around conservative websites that the IRS lost seven hard drives, and WHAT ARE THE ODDS?!?! This is supposed to be some indication of nefarious intent on the part of Lois Lerner and the Obama Administration to cover up an illegal targeting scheme directed at conservative non-profit advocacy orgs. If anybody can find a definitive source for the seven hard drives claim, one that comes from a real newspaper and not a wing nut blog I’d much appreciate it. For now I’m simply going to address the statistical likelihood that the IRS might have such a number of hard drives crash on them during the time period at play.

Turns out there’s a wide disparity in the reliability of hard drives, which varies by both make and model. A recent Backblaze study, detailed in Ars Technica, put the failure rate roughly between 1 and 24 percent per year. So let’s be incredibly generous and assume that the IRS buys the best Hitachi drives and that in that enterprise environment they last at their best test failure rate of 1% annually.

The IRS has 85,500 employees. Again, lets be generous to the conservative claims and assume that only one in ten IRS employees has a computer with a hard drive, that’s 8,550 drives in the entire org, a ridiculously low estimate for an entity as large as the IRS. That means that, at the absolute bottom end of estimates, in any single year one should expect the IRS to have at least 85 drives crash while in service.

Now, from what I’ve heard these seven or so drives were all in different computers assigned to different employees, and they failed over a timeframe of two to three years. So we really need to gauge the odds of seven failures against an expected loss of at least (and again being conservative) 170 drives IRS wide. Again, this assumes that only one in ten IRS employees has a dedicated computer and completely ignores the vast arrays of hard drives that make up the IRS data storage centers.

Everything I’ve done here was to give the biggest benefit of the doubt possible to those who claim that the loss of seven hard drives is some kind of mathematically near impossible event. However like many claims that revolve around a single number completely devoid of context, it doesn’t hold up to honest scrutiny. As you can see, the claim going around conservative websites doesn’t even take real statistical analysis to debunk, simple arithmetic destroys it.

P.S. So far this article from The Hill is the only real source I can find on the seven hard drives claim:

The two Republicans have said that the IRS can’t produce emails from six other officials, further threatening their investigation.

“We need to know where these computers are, who looked at them and when,” Camp and Boustany said in a Wednesday statement.

This would confirm the notion that we’re talking about six different unnamed people, who have totally unstated ties to the investigation outside of being IRS employees.