Barter relationships are often cemented with a yapa:a little bonus given to the buyer that takes the form of an over-reciprocation to assure future transactions (Browman 1990: 421;Sahlins 1972: 303). The magical powers attributed to the yapanotwithstanding, Sahlins' (1972: 308-314) develops a functional economic explanation for over-reciprocation where it serves a similar mechanism to price fluctuations in market-based societies. When an over abundance of product A relative to product B exists in a barter situation based on traditional equivalencies (hence, a lower value for A may result, in a market system), the provider of product A may over-reciprocate and thus, based on the morality of reciprocal arrangements, guarantee future compensation from the trade partner.

The primitive trade partnership is a functional counterpart of the market's price mechanism. A current supply-demand imbalance is resolved by pressure on trade partners rather than exchange rates. Where in the market this equilibrium is effected by a change in price, here the social side of the transaction, the partnership, absorbs the economic pressure. The rate of exchange remains undisturbed - although the temporal rate of certain transactions may be retarded (Sahlins 1972: 311).

The discrepancy that must be resolved synchronically in neoclassical market economics is resolved diachronically in reciprocal arrangements (Danby 2002). Browman (1990: 421) does not believe the over-reciprocation device described by Sahlins is in evidence in the Andes. As Browman observes, there is ethnographic evidence that suggests that barter rates do, in fact, fluctuate in response to supply and demand. The arrangement described above is one possible configuration that occurred in prehistoric circumstances, however, and it is a possible means of assuring the long term persistence of exchange relationships (Burchard 1974;Mayer 1971).