Provide per-country graphs for multiple countries at once
We have a few graphs showing statistics per country. We should allow users to select multiple countries to generate a graph with statistics for all selected countries.
The first question is how an intuitive interface for selecting multiple countries would look like. Is a multi-select list box with 247 entries even manageable? What other options are there that don't require JavaScript?
The next question is whether lines should be drawn in different colors using a single y axis or as multiple stacked y axes. The former makes it easier to compare absolute numbers to each other, the latter allows to compare trends even if absolute numbers have different orders of magnitudes. Both approaches are probably limited to something around 5 countries at a time before graphs become incomprehensible. Of course, we might offer the user to select one of the graph types without much additional effort.