The data is interesting, but I am always skeptical of self-reported sleep times. It seems there is a sense of pride some people take in sleeping less than others.
"Our model suggests that persons sleeping 5 and 7 hours over-reported, on average, by 1.3 and 0.3 hours respectively."
For self-reporting sleep studies, perhaps people have it in their head that 8 hours is how much they're "supposed" to sleep and they over-report to better match that?
Of note, however, while the CDC data I linked comes from the Behavioral Risk Factor Surveillance System which does appear to be merely a self-reporting survey question (https://www.cdc.gov/sleep/surveillance.html), the data in the Economist article comes from an app (www.sleepcycle.com). Granted, I suspect the latter almost surely suffers from some kind of non-trivial selection bias.
Would be interesting to look at smart watch data to see actual averages. You can tell when a person is sleeping by watching their motion activity (obviously) in combination with a drop in heart rate.
