It was a sample. Wansink's conclusion wasn't that the Joy Of Cooking got fattier, it was that home cooking got fattier, and Joy of Cooking was a proxy for that.

It was a sample. Wansink's conclusion wasn't that the Joy Of Cooking got fattier, it was that home cooking got fattier, and Joy of Cooking was a proxy for that. So it was a sample from the larger universe of home cooking.