The chart (currently; it might have been updated) does show both reported GDP and light-at-night inferred GDP for "free" economies. The article doesn't say exp

The chart (currently; it might have been updated) does show both reported GDP and light-at-night inferred GDP for "free" economies. The article doesn't say explicitly, but we must assume they're using a linear mapping between the two, since there are minor discrepancies in the "free" economies (as one expects with necessarily noisy data).