Say you were using one UA-ID for half a year and switched to another UA-ID in the second half of the year. How can you calculate the overall average bounce rate for the whole year? As far as my math goes, you can't average two percentages. One would need absolute numbers, so this got me thinking that maybe I can calculate the total bounces (not the rate) for each UA-ID, add them up, and later divide by "something" to get the "average" bounce rate over the two tracking ID's. Is my reasoning correct? If so how do I do this using the metrics supplied in Google Analytics? Or is there another way to calculate this?