It's difficult to see it any other way. Leaving out 5 countries from the average, weighting one year of New Zealand to 19 years of the U.K... this looks pretty foul. In this day and age, all publications should come with the original dataset.
Yet because there are only 7 data points possible, it completely changes the result. This is a very high profile economic report coming from two very influential Harvard economists. Consider that they accidentally left out their -7.9 data point from New Zealand:
Not only does removing the NZ data point instead make the average much higher, the data looks more reliable than the full dataset as the standard deviation has almost been cut in half. Leaving out one data point from such a small set has big consequences. Their 6 data points: ave: -0.07, s.d.: 3.83
All 7 data points: ave: 0.26, s.d.: 3.67
No NZ data point: ave: 1.43, s.d.: 1.73