This is an amazing MIT project:
The Billion Prices Project is an academic initiative that uses prices collected from hundreds of online retailers around the world on a daily basis to conduct economic research.
As Tim Harford points out, the project arose from Argentina’s official determination to prevent inflation data being reported:
But one economist found a way to publish plausible inflation statistics without being prosecuted. His name is Alberto Cavallo, and he realised that by gathering price data published by online retailers, he could produce a credible estimate of Argentine inflation from the safety of Massachusetts. Cavallo’s estimate averaged more than 20 per cent a year between 2007 and 2011; the official figure was 8 per cent.
So began the Billion Prices Project and its commercial arm PriceStats, both collaborations between Cavallo and fellow MIT economics professor Roberto Rigobon. “Billion Prices” sounds hyperbolic but that is the number of prices collected each week by the project, from hundreds of retailers in more than 60 countries.