Our Happiest Age

Today I stumbled on to an interesting website displaying a graph that relates survey answers of believed or expected happiest age to age of the responder. The data were made available and above is a scatter plot with a best fit line and 95% prediction bounds.

While the R-square is low (0.1354) the positive relationship is very highly significant, as the 95% confidence interval for the slope of the fitted line is (0.3688, 0.5481), which obviously does not include 0.

This means that as people get older, their stated belief regarding the best year of their life increases. While this initially struck me as reflecting optimism, the fact that the slope is less than 1 means that at a certain point people begin to believe that their best year is behind them. This happens at age 27-28 on average. Earlier than that people think their best year is ahead of them.

I'm 28 years old now, so I guess I'm supposed to believe that this is the best year of my life. In truth, the data are so variable that 95% of the time I would believe that the best year of my life is somewhere between 2 and 53, which is a huge range.

While it's sad that we become less and less optimistic with age, the good news is that according to this fit line and prediction bounds, the time when one's current age creeps outside the 95% confidence intervals for their believed happiest age is 74. After that at least 95% of the time people think their best year is behind them.

This figure simply shows the mean and standard error of those responding. The overall average expected "best year" was age 31 (sem 0.55). The average age of those responding was 35 (sem 0.44).

As a final note, these data are not quite normally distributed (both in terms of age of responder, and in perceived best age), but are pretty close.