Mother Jones has a piece today about whether British Petroleum will own up to the amount of oil it spewed into the Gulf. (I have clarified wording here based on reader comments.)
This controversy raises one of my pet peeves as a technically-trained person. Most reporters aren’t numerate, and it shows.
Often this innumeracy reveals itself in small ways, often in economics or budget stories since these are most likely to involve actual numbers: errors with percentages, confusion about basic financial calculations involving interest rates. Sometimes innumeracy shows itself in other ways, such as believing transparently implausible numbers in specific news stories.
The Gulf spill provides an especially depressing example because this was such a huge and well-covered story. British Petroleum and the government stated that 5,000 barrels per day (***See comments below. My commenters are right to call me for sloppiness here. ***) were leaking into the Gulf. This never made any sense. Bear with me, while I perform a sloppy but revealing calculation that demonstrates why.
There are 42 gallons in a barrel. So this 5,000 barrel figure is equivalent to 210,000 gallons per day. That seems like a big number–until you recall that there are 86,400 seconds in a day. So one would have to believe that a gushing 20-inch-wide pipe was releasing oil at a rate of 2.4 gallons per second.
Is this a little or a lot to be flowing out of a 20 inch pipe? As you recall, the area of a circle is pi-r-squared. So the cross-sectional area of that pipe was about 314 square inches. As you may not recall but could google, a gallon is about 231 cubic inches. So a flow rate of 2.4 gallons/second is about 561 cubic inches per second. This implies fluid would have to be moving through the pipe at a corresponding rate of about 561/314=1.79 inches per second. How fast is that? Since there are 12 inches in a foot, 5,280 feet in a mile, and 3,600 seconds in an hour, you can verify that this flow rate is about 1.79*3600/(12*5280), or …. 0.1 miles per hour. If you saw the live shots of oil gushing out of the Deepwater Horizon, you know this couldn’t be right.
Of course my sloppy ballpark calculation could be pretty far off. The diameter of the pipe might have been slightly smaller. Perhaps the flow was partly blocked. Suppose I left out enough to bias the calculation by a factor of 5. That calculation would still indicate that either (a) BP’s estimate was transparently implausible, (b) other junk was flowing out of the pipe alongside the oil, or (c) some combination of (a) and (b) were both true.
When experts challenged these estimates, reporters treated this as an esoteric matter or a murky he-said, she-said dispute. It wasn’t. (Kudos, though, to NPR for this story.)
It’s telling that even on the most extensively-covered pollution story of the decade, these rather obvious points were so rarely communicated.
Postscript As noted, my commenters are right to call me on this. That 5,000 barrel/day estimate was actually an initial figure embraced by the government. Reporters should have been less credulous in questioning both the government and BP on these points.