Formal and Informal Markets: A Strategic and Dynamic Perspective

In formal markets, to attract buyers, sellers must publicly advertise their prices and locations. But in informal markets, sellers must remain anonymous from government authorities. Since agents' payoffs depend on the ratio of buyers and sellers in each of these markets, all agents try to position themselves in the market which can yield them the highest possible payoff. This strategic interaction in turn critically affects the time evolution of these two markets. In our benchmark model, in which only sellers can switch between these markets, there exists a unique stable dynamic equilibrium where formal and informal markets co-exist. Sellers switch from the formal to the informal market whenever costs of trading in the informal market decrease, and vice versa. In a richer environment, where both sellers and buyers can switch between markets, and the sellers' and buyers' costs of trading in the formal market net of those in the informal market have opposite signs, there exists a unique stable dynamic equilibrium where formal and informal markets co-exist.