Looking for “elbows” in a noisy time series with relatively few points is a pretty easy way to get spurious results. If the 1960-62 obesity number was overestimated by 2 points and/or the 1976-1980 number was underestimated by 2 points, it wouldn’t look like 1976-1980 was a special transition at all.
(And clearly errors of that magnitude happen, unless you think there’s a deep reason why obesity rates were nonmonotonic from 2005-06 to 2011-12.)
That’s true, I just think that seeing an elbow is more compatible with there being an actual elbow than there not being an elbow. It’s not definitive, just interesting and potentially worth further study.
Looking for “elbows” in a noisy time series with relatively few points is a pretty easy way to get spurious results. If the 1960-62 obesity number was overestimated by 2 points and/or the 1976-1980 number was underestimated by 2 points, it wouldn’t look like 1976-1980 was a special transition at all.
(And clearly errors of that magnitude happen, unless you think there’s a deep reason why obesity rates were nonmonotonic from 2005-06 to 2011-12.)
That’s true, I just think that seeing an elbow is more compatible with there being an actual elbow than there not being an elbow. It’s not definitive, just interesting and potentially worth further study.