How To Cherry Pick Data

In his post “Senate Republicans Block Targeted Jobs Relief for Teachers And First Responders“, Matthew Yglesias points out that “during the Obama years” private employment has rebounded while government employment has seen a “sharp contraction”.

Yglesias points to a couple of charts, but I’ve helpfully replicated his data set into a single chart, because that’s just the kind of guy I am.

As you can see, using January 2009 as our point of reference, private jobs have rebounded from a drop of 3.79% in 2010 to a drop of 1.63% in August (my data is slightly out of date, but good enough for gov’t work… get it?!?). Local gov’t employment has fallen 3.6% in that same time frame. I also added federal gov’t employment (which has fallen 2.75% since January 2009) for the heck of it.

In the comments section, Peter Schaeffer complains that Yglesias is cherry picking the data and points out that gov’t employment saw +10% gains in the decade leading up to the crash and 3-4% losses from the peak while the private sector saw slightly less than 5% gains in that time period and slightly more than 5% losses from the peak.

I thought that Schaeffer had a good point, but needed some visuals to drive it home, so I thought I’d show Yglesias’ jobs data in Schaeffer’s context.

As you can see, Yglesias’ data starts at a really handy place for his argument, since it begins measuring job losses and growth at a time when we had already seen drastic private sector losses, but no public sector losses.

Of course, the funny aspect to this data is that one could use it to say that President Obama is reigning in the public sector that George W. Bush let grow out of control. I think the only reason no one is saying this is because everyone on President Obama’s side would consider that a bad thing and everyone who opposes President Obama would consider that a good thing. Neither side really wants to attribute this trend to President Obama. In fact, President Obama is working actively to reverse this trend.

Ah, the little ironies of life.

Note: In the spirit of “never attribute to malice what can be explained by incompetence”, I wouldn’t be surprised if Yglesias unwittingly cherry-picked the data. “The Obama years” is a perfectly rational place to start looking at data and, if that was the only data you looked at, it would support his conclusion. On the other hand, Yglesias has always had a better grasp of the data than this particular post suggests, so I suspect he kind-of-sort-of knew that this was a cherry picked sample set but was OK with using it because it bolstered his argument.

13 comments

  1. Andy Geer says:

    “Why” is perhaps more important. Much like 2008, the outcome of the November 2010 election was known several months before. Everyone knew that Republicans would stop the government gravy train and would try to be more private-sector friendly. Do you think that had any effect? Thanks.

  2. politicalmath says:

    This is a guess, not based on any real evidence: Government revenues are going to lag behind economic realities at least somewhat. My guess is that local revenues (which are largely dependent on property taxes) are going to lag a number of months behind the economic realities so that local and state gov’ts aren’t going to feel the sting until sometime after the crisis hits.

    Add to that the fact that a very large chunk of the initial stimulus went to propping up local and state departments and it means they were able to hold on to their employees longer than private employers. As the stimulus wound down, they could see the writing on the wall and started laying employees off or encouraging retirements.

    But this is all speculation on my part. If you see anything that resembles real evidence, I’d love to see it.

  3. […] forward to yesterday, when Matthias Shapiro caught Yglesias in some data visualization sleight-of-hand: In the spirit of “never attribute to malice what can be explained by incompetence”, I […]

  4. BooksMoore says:

    Well, the Obama years is, in fact, a perfectly rational place to start – by way of reaction. Yglesias is seeking to counter the idiotic notion that the one sitting president is responsible for the total sum of the economic picture. That notion, obviously, begins when Obama took the oath of office. So naturally, Yglesias also begins his argument there.

  5. Thanks, Matt! Great clarification.

    We’ve been trumpeting this as much as we can at ReasonableViews.com. Our “Double Dip or Lost Decade” article focused on the blue line, pointing out that we are below where we were 11 years ago. There’s no period since the Great Depression when something like this was true. The key point in my mind is that the growth after the ’01 recession was so meager that it was wiped out entirely by the next recession. Add to this that wages are down in real terms and the stock market is down since 2000, and you have a disastrous decade. I suspect that most people don’t step back enough to realize how bad the last 11 years have been, and I think we need to explore and understand the issue before we can solve it.

    Thanks,

    Jim & Evan
    http://bit.ly/sSCZjN

  6. Michael Fisk says:

    @BooksMoore:

    That being said, saying “I took office after the worst of the private sector job losses had abated and still their numbers are off from where they were three years ago at the tail end of a recession” is not much of a credit to the administration either. (That being said, assuming a roughly linear pace for private sector job gains from their recent uptick in 2011, they’ll be poised to get to January 2009 levels about in time for the 2012 election. Say it with me: “Lost Decade”.)

  7. doug says:

    So what special about the 2000 start point? It would be instructive to see the curve since 1950 or 1900, or since the data was collected in a robust fashion.

  8. jorod says:

    Talk about cherry-picking data, ever read this blog?

  9. ryan says:

    This is horrible. Want to learn how to actually cherry pick http://www.shvoong.com/how-to/careers/2029954-cherry-pick/

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  12. […] finally contracts. You can always take a snapshot of only the period of lagged decline (the far right portion of the chart), ignore what went before, and say “see, the public sector is dangerously shrinking.” […]

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