It doesn't take into consideration changing borders. For example on 1800 much of the World belonged to Britain (eg, the biggest example India). Switzerland didn't exist in 1800, so how could you have population data for it? Only in 1861 was Italy unified.
Oh come on. Firstly targeting Apple, when it is obviously a social issue. Secondly, targeting a device, rather than the wider issues. Like housing cost, salaries, uncertainties in general.
It is a really nice website, but you are misguided: averages exist for a reason. Would you choose a location because last year it was the perfect temperature (even though the past ones all said no)?