Hi, I did not have a change to participate in a review because I was busy at the time(as it is usual lately). I did like the submission when it originally appeared. And now after reading docs some more I could only congratulate Eric for yet another good addition to the boost. Being the author of similar (though obviously not that powerful) component myself I find two featured omitted. I must admit that I may've easily missed something. But here we go. 1. accumulator composition It would be a pity if I need to write new accumulator any time I need to combine features implemented by two existing one. For example min/max average value min/max change rate 2. timing policy. In many of my real life projects that require some statistical value it almost always need to be combined with the time of the event. For example when particular value reached it's maximum? when particular value reached it's minimum? when particular value was last changed? or more specific: When 10 sec throughput average reached it's maximum? similar idea could be applied to any statistics that model some extreme value. IMO framework should support this in a form of timing policy somewhere. Another general comment. I personally would find single changing variable oriented interface more convenient and ore widely applicable (as opposed to the samples set). Variable could change in many ways (not only addition or subtraction, and even those could be done more conveniently with operator overloading). Essentially what I am looking for is something like this: tracked_var<....> v; v += 10; int i = v +1; v -= 5; v *= 2; cout << average( v ); cout << max( v ); cout << min( v ); cout << max( average( v ) ) << " @" min( average( v ) ).time(); Regards, Gennadiy