There are a number of measurements used to discuss cost of living, including inflation, Consumer Price Indexes, Purchasing Power Parity, Personal Consumption Expenditures Price Index, etc. Some of the best resources for this kind of data are:
The OECD iLibrary includes multiple relevant data points in its 'Prices' indicator section (including PPI, CPI and inflation)
The American Institute for Economic Research has a Cost of Living Calculator, if you'd like to look up how the value of money has changed over time. They also publish regular research reports on the topic of inflation, etc.