Budget Update: Weapons of Math Destruction(+)

CalPundit has an explanation, of sorts, for Bush’s untrue statement about discretionary spending:

[referring to a chart in Bush’s budget titled “Percent Change in Discretionary Budget Authority] … discretionary spending outside of defense and homeland security went up 15% in 2001. Or rather, that discretionary spending authority — not actual spending — went up 15%. See, he was just speaking in a kind of shorthand, that’s all.

But even if that’s what he really meant, you may be thinking that it still doesn’t make any sense. After all, if total discretionary spending went up only 5.5%, how is it possible for his chart to show all three separate components going up by that much or more? Klingon math?

I too am curious about how the numbers 5%, 14%, and 15% (respectively, FY2001 growth in defense, homeland security, and non-defense/non-homeland discretionary spending) can average out to 5.5% (the overall growth of discretionary spending in 2001.) Mathematically, it’s possible, but a quick calculation shows that for this to be true, roughly 95% of 2001 discretionary spending must have been on Defense (*). I don’t buy that. In fact, Josh Clayborn’s second figure in this post shows that defense spending accounted for less than half of total discretionary spending in both 2000 and 2001 (2000: $305b of $637b; 2001: $308b of $665b) — again, flatly contradicting Bush’s statement.

In almost plain English, this means that if (1) defense accounted for 95% of discretionary spending while other stuff accounted for 5% of discretionary spending and if (2) defense grew at a 5% while other stuff grew at 14 to 15 percent, then and only then would the overall rate of discretionary spending growth be 5.5%. The numbers don’t add up.


(*) I compute this by lumping homeland and non-defense/non-homeland spending together as growing at roughly 14.5%. Defense grew at 5%. So if, from 2000 to 2001, 95% of total discretionary spending grew at 5% and 5% of total discretionary spending grew at 14.5%, then the weighted average is 0.95*(.05) + .05 (.145) = 5.48%.

(+) The title is from commenter Pierre at CalPundit; it was too good not to use.