ARTICLE: How to Mislead With Statistics: GMO Crops Edition

The following is an excerpt of a November 2nd, 2016, article by Kevin Drum in Mother Jones correcting some of the misinterpreted figures in a recent New York Times article. 

A few days ago the New York Times ran a big front-page story about GMO crops. Roughly speaking, there were two takeaways: GMO crops don't improve yields and don't cut down on pesticide use. So why bother?

That sounded interesting, but I decided not to write about it. The story was pretty shallow in its use of statistics. It assumed that you can compare different countries without controlling for anything (different soils, climates, crops, etc.). And it seemed to suggest that American farmers must be idiots, because they keep buying GMO seeds even though they're worthless. Put together, this was a little too much for my spidey sense, and it would have taken a long time to educate myself enough to really figure out what was going on. So I passed.

Yesterday, however, Nathanael Johnson of Grist took a close look at the Times piece and concluded that it was pretty misleading. You can read Johnson's piece if you want all the gory details, but it contained a pretty interesting example of how to mislead with statistics, which I figured I should pass along. The Times story says that in the US, despite the wide use of GMO seeds, use of insecticides has fallen but the use of herbicides has gone up. In France, by contrast, where they don't use GMO seeds, "use of insecticides and fungicides has fallen by a far greater percentage — 65 percent — and herbicide use has decreased as well, by 36 percent."  Using data from Andrew Kniss, here's what this looks like in chart form:

It does indeed look like France is doing pretty well. But what if you look at the raw numbers, rather than percentages? Here's a chart from Kniss:

In the case of herbicides, France started at a high level, and has only recently caught up to the US. In the case of insecticides, France started out way, way higher than the US and is still way higher despite their recent reductions. Looked at this way, it's clear that France hasn't actually done that well. What's more, I had to cherry pick starting and ending years in the top set of charts in order to make France look as good as it does.

To read the entire article, please visit the article at the Mother Jones site.