Consider an industry in which FOUR firms compete in prices with an infinite horizon and a discount factor . All firms have a constant marginal cost of c. Initially, total demand in the industry is D(p) but demand is growing every period by a growth rate of g>0. This means demand in the next period is (1+g)D(p), demand in the following period is (1+g)² D(p) and so on.

Consider a subgame perfect equilibrium of the infinitely repeated price game in which firms charge the monopoly price and use trigger strategies with indefinite reversion to the static Nash equilibrium.

Assume the growth rate is g=1/4.

What is the lowest value of the discount factor for which collusion can be sustained?

[Give a number between 0 and 1 with a maximum of two decimals.]