The principle of aggregation is to maximize bandwidth by taking advantage of the multiplexing ability of the network. In theory, 1 + 1 = 2. However, splitting and merging the data stream in Internet bonding creates additional data traffic. Therefore, in the case of internet bonding, 1 + 1 = 2 is not. The best aggregation that can be achieved is around 1.5. So 1 plus 1 equals 1.5 in the best case.
You can find more about bonding here: Internet bonding service