Calculating Total/Sum/Average of dispersed values across the network

How to calculate SUM of values stored at different nodes in the network? Since it’s global, critical to find where nodes never store all the data coming from the authors, since no master chain. If CRDT like technique will be implemented for this, then where to find such global values; at a single node in the network? Then, the same centralization issues will arise. So,how can we handle this?