Annals of Bad Math (with update)

This popped up on my facebook feed today, posted by OccupyDemocrats (of course,) and is an incredibly fabulous example of bad math.

Here's the WaPo link.

What WaPo says:
The finding comes from a government study considered a gold standard to measure public-health trends. Researchers found that just over 8 percent of children 2 to 5 were obese in 2011-2012, down from nearly 14 percent in 2003-2004. Although the drop was significant, federal health officials noted that obesity rates for the broader population remain unchanged, and for women older than 60, obesity rates rose about 21 percent during that period.
And here's the JAMA article link.

What JAMA says:
There was a significant decrease in obesity among 2- to 5-year-old children (from 13.9% to 8.4%; P = .03) 
So, did you see what Occupy did there? They took the rounded up 14% and the rounded down 8.4% and did this: (14 - 8)/(14) = 0.4285. Then claimed that was a decrease in obesity of 43%!!! It's: 13.9% - 8.4% =  5.5% drop in obesity among 2-5 year olds, not 43%.

However, here's another problem. Obama's big push has been to change the composition of school lunches, but the drop in obesity has been among pre-school aged kids. How exactly can she take credit for that?

Update: Apparently, this began with bad math from the New York Times back in February of 2014 in an article written by Sabrina Tavernise:
Federal health authorities on Tuesday reported a 43 percent drop in the obesity rate among 2- to 5-year-old children over the past decade, the first broad decline in an epidemic that often leads to lifelong struggles with weight and higher risks for cancer, heart disease and stroke.
[...] But the figures on Tuesday showed a sharp fall in obesity rates among all 2- to 5-year-olds, offering the first clear evidence that America’s youngest children have turned a corner in the obesity epidemic. About 8 percent of 2- to 5-year-olds were obese in 2012, down from 14 percent in 2004.
The article remains on their website, uncorrected, with the wording above (as of 7/6/15.)

Slate blasted the NYTimes piece  (corrected Salon to Slate. 15/08/23) back when it came out:
A far bigger issue is that studies like these, and the headlines that result, drive the discussion about public health and policy in this country. The media seizes on sexy results, amplifies them without due skepticism, and the public is misled. This can impact billions of dollars allocated to campaigns meant to capitalize on the supposed implications of scientific studies. It's hardly an academic footnote in this case. Commentators are already attempting to adduce the reasons for the decline in obesity in this age, pointing to the dietary changes in preschool menus, awareness campaigns, and exercise programs that specifically target tots.