The evolution of monetary frameworks in 25 advanced economies since 1974. Following the demise of the Bretton Woods system, exchange rate and monetary targets have gradually dissapeared, to be replaced by inflation targets.
The data is from research by David Cobham, and is avaiable at the Monetary Frameworks site.
To make the chart I summed across all the detailed types of framework that Prof Cobham has identified, and focused on advanced economies only. The data used in my chart is here and the code to draw the chart is here.