It highly depends on the interests of the end user whether the (for example) the activity metrics for the last week, month or year are relevant, or whether it is relevant to compare the last two years or the last two weeks. It would be great if the user could select this aggregation parameter dynamically and let the client or server compute this final (computationally simple) aggregation over the basic metric providers dynamically.
Perhaps there are good visual metaphors for this time granularity, i.e. a sliding selector over a time bar?