How should we display the "like for like" percentage open?

[pwalsh]

I added a calculation for percentage open "like for like". It takes the list of places in the "base year" of an Index (2013 in Global case), and calculates % open using these places only in forward years.

This data is not currently available to users of the site.

Example:

On the global index, percent open in 2013 is 15%, percent open in 2014 is 11%, and percent open like for like in 2014 is 15%.

[Stephen-Gates]

As a suggestion, on a page like http://index.okfn.org/place/australia/, you could complement "See Other Years" with "Compare to Other Years" to allow comparison of any year with another.

[pwalsh]

@morchickit this is the issue that supercedes #75