Wednesday, November 24, 2010

The Further You Extrapolate, the Sillier You Look

I'm always bemused by graphs that try to extrapolate too far.  Case in point at right (found by Darren).  The numbers previous to today are obviously known well but the future is a little cloudier.  Nevertheless, this graph claims to see a trend going rather upward, even though the trend for the next few years is downward.

Like the "population bomb" scare stories of the recent past, this one is just silly.

Why silly? Because it assumes that "given no change in policy, the numbers will do this."

Given no change? This is America.  We can't stop changing. The one thing that will never happen is steady state.  Somebody will introduce a bill to change this or that and your whole projection becomes worthless ... as if it meant much to begin with. We adapt in this country.  When the deficits were spiraling out of control under Reagan/Bush I, the country adapted, we nearly balanced the budget and we were starting to work on the debt.  Clinton's policies were less of a driver than the tech boom but, c'est la guerre. I'm frankly surprised that the National Review published it because it shows the sharpest drop under Obama's second term.

I had to tweak Darren, since he's a staunch conservative:

"Come on. Extrapolating a possibly exponential curve out to 2082? You really shouldn't, as a math teacher, have let that go without some comment. 

But I'll play along ... let's read the graph. The percentage surges upward in 1980-1984 when Reagan was doing those enormous deficit budgets -- to drive the Russians to bankruptcy, yes, but it still increases.

Then the economy recovered and those percentages dropped under Clinton (not that he was totally responsible for that, but it does make a good way to tweak conservatives!).  Likewise, the percentages rises under GWB, hits a peak in 2010 under Obama, and then shows a tremendous downward slope under the remaining years of Obama's term (and into his next?). Then, in 2016 (when the Republican presumably gets elected), the percentage starts to climb again.

I'm not sure that's exactly what you had in mind."

Darren responded later ...
"It's when the health care costs really start to kick in. Of course extrapolations that far out are silly, which is one of the reasons why I love the global warmers so much. Still, I don't see anyone arguing that our interest payments are going to go *down* any time soon."

No. But why is that graph any less ridiculous? The spending by Government is totally under the control of the Legislature and can be adjusted yearly as the political winds blow. If they wanted to, the Afgan war could cease in days, the bailouts could stop, the contracts could be ended and penalties paid.

Global warming isn't quite up to a vote by the House Ways and Means Committee. Natural processes don't stop on a whim.

I don't particularly care about the gloom and doom part of the debate anyway, so I'm probably not a good person to argue this with. I don't care about global climate as such, but I do care about MY air. If NYCity goes under water, it'd be turned into a modern Venice pretty quickly and Mankind would adapt. Florida would build dikes like Holland and Mankind would adapt. Ideal croplands would be found further north and, well, you get the idea.


  1. I notice you didn't print my response, though. Bummer.

  2. A matter of timing! I'll add it in.