You’re certainly familiar with Wikipedia, but you may not be aware of Wikidata, which is an ongoing effort to structure some of the data underlying Wikipedia. Traditionally, facts (e.g. the population of New York City) are embedded in the text of a wiki, and there’s no easy way to automatically extract them. Wikipedia has a little more structure than this, but it’s still really designed for humans rather than machines.
Wikidata is the opposite – designed for machines, not humans.
It’s part of the broader semantic web movement, which aims to make the web more and more machine readable. Most of the time you don’t notice this, but when you run a query like “spouse of George Washington” and see this, rather than just a collection of links, that’s Google taking advantage of semantic web data (probably – they might also be using machine learning to infer it from unstructured text).
Many economic statistics seem conceptually simple, but are rather intricate and technical as actually measured (or more accurately, constructed). You can’t just line up dollars of GDP and count them. Price indices are similarly fiendish.
Conceptually, the purchasing power parity exchange rate between two countries is simply the relative cost, in local currency units, of buying the same basket of goods in each country. This can be very different from the market exchange rate, but is generally a better way to convert, say, GDP per capita, if you’re interested in cross-country comparisons of welfare (GDP? welfare? we’re already on shaky ground…)
Last week another Australian I know in DC was surprised to see that the International Comparison Program’s (ICP) 2015 PPP exchange rate for Australia is 1.487. Are things really 50% more “expensive” (dollar for dollar) in Australia, he wondered?
In the last week I have found myself arguing both that murder statistics should be expressed as population rates and that doing so can be quite misleading. That kind of apparently inconsistency deserves a quick explanation.