Even more pedantic, but surplus allocation is typically determined by the board of the co-op. While it's probably generally true that this functions a bit like a representative democracy, I have definitely been a member of (and worked for) cooperatives where the board is not exactly aligned with the membership about how to allocate surplus funds. Typically this comes when the co-op's board wants to make a capital investment for long-term growth when the membership may want their discount/dividends/whatever-the-organizations-payout-structure-is more than they care about expanding the scope or mission.