This is largely based on Mike Bostock's Stacked-to-Multiples gist. I have added 4 snippets to the original code in order to represent the magnitudes of each group per quarter and also each quarter's total. I find totalling the values as they are stacked to be an efficient and intuitive way to marry visual movement with enhanced information display.
fernoftheandes
Except for the code segments that render the magnifying glass (as circle or path), this is essentially a copy of Mike Bostock's Fisheye Distortion example.
The motivation for this was largely aesthetical but also a bit functional. When using the Fisheye as an aid to viewing large datasets, I often find myself experimenting with the degree and radius of the distortion. In such cases, I find it helpful to see the exact reach of the distortion and then decide the best configuration for a particular dataset.