Crunching the numbers

Tuesday, I linked to a post by conservative economist Greg Mankiw, in which he gloats that conservative breeding success will lead them to overwhelm liberals at the voting booth.

The article that prompted the gloating by Prof. Mankiw was this OpinionJournal article by Arthur C. Brooks, a professor at Syracuse University. In this article, Prof. Brooks claims

Alarmingly for the Democrats, the gap is widening at a bit more than half a percentage point per year, meaning that today's problem is nothing compared to what the future will most likely hold. Consider future presidential elections in a swing state (like Ohio), and assume that the current patterns in fertility continue. A state that was split 50-50 between left and right in 2004 will tilt right by 2012, 54% to 46%. By 2020, it will be certifiably right-wing, 59% to 41%. A state that is currently 55-45 in favor of liberals (like California) will be 54-46 in favor of conservatives by 2020--and all for no other reason than babies.

Steve Reuland at Sunbeams from Cucumbers wonders what sort of newfangled conservative math Prof. Brooks is using to make his calculations:

You don't really need to do the math to know that this is certifiable nonsense. But let's do it anyway, starting with Ohio. It's a fairly simple thing to see if we can start with Brooks' assumptions and end up with his results.

The population of Ohio is roughly 11.4 million. In 2002, there were 159,192 births, and 111,550 deaths. Assuming those numbers haven't changed much, and that they'll remain the same going from 2004 to 2012, that would be 892,000 Ohioans that will have died between those years, and 1.27 million that will have been born. We'll ignore the fact that some of those being born will also be the ones who die. What this basically means is that the total population in Ohio in 2012 (ignoring migration -- more on that later) will be roughly 11.8 million, 10.5 million of whom were alive during or before 2004.

If those 10.5 million were split 50/50 between liberal and conservative, and the 1.27 million extras are split 41/59 between liberal and conservative, how much would this change the overall split? We can just multiply the numbers by the percentages to get the totals. We get 5.77 million liberals and 6 million conservatives in 2012. That's less than a 49/51 split. For all practical purposes, unchanged.

How the living hell does Brooks come up with a 46/54 split? I'll have to email his ass to find out.

Personally, I don't see the point of gloating about the supposed demographic success of one's political faction, since this obviously has nothing to do with the inherent superiority of one's political position.

But if you're going to gloat about it, you should at least get your numbers right.

(Via PZ Myers.)