View it better wider at Google Fusion Tables
Select the handles at either end of the bottom bar to zoom into a particular time period. Full Names for initialed parties below.
This time series is much Better then ManyEyes Stack chart I blogged last night.
It positions the years properly,shows you the party numbers at the key points, you can select the governments, I like it Shows CnaG trailing off and then Fine Gael picking up the line a few years later. Like to have it shaded in and with percentages, I now have all the info and will make that later along with making a timeplot for more customization.