To a degree this is true, but they do find the abundance of some "amenities" negatively correlated with national income, some of which, like "marketplace" make more sense than others (like "hospital", at least until you consider not all hospitals are equal and the state of the art ones tend to be big...). When it comes to ATMs being more commonly depicted in lower income countries (within the sample) it's an interesting question whether that's because they actually are more common or whether they're more commonly marked on OSM because locating them is more important to people in a cash economy (cf most of the ATMs near me are unmarked)
>like "hospital", at least until you consider not all hospitals are equal and the state of the art ones tend to be big...
I'm willing to bet this and possibly some of the other amenity correlations are driven either by a few outliers, some uncontrolled confounding variables, or by measurement error.
E.g. if one of the poorer nations has a strange policy or linguistic quirk around the definition of hospital, that could be driving up the total number of locations marked as hospital and thus introducing some hidden bias.
In terms of confounding variables, I'm just taking a guess in the dark, but hospitals per capita is probably a strong proxy measure of how rural a country is. The more rural the population, the more hospitals are required to serve the same number of people, because hospitals need to be close for emergency situations.
Also, there's probably a selection bias. Hospitals are likely one of the first things to get put on OSM for a given area. Because there aren't many of them and they tend to be one of the most important items people are looking for on a map. So poorer countries, with fewer OSM users, are more likely to have hospitals marked relative to the other amenities.
Meaning, you could have a negative relationship between all amenities and GDP/GNI/HDI, but only hospitals and other items consistently marked across all countries is being measured well enough to demonstrate this. Even though naively one might assume more amenities/person is better, it's possible for many amenities that centralization/consolidation actually correlates with better economic performance. Obviously that's probably not true of park benches, but it might be for schools, hospitals, and other public infrastructure.
