“…Among the many formal analyses of the merits and drawbacks of price-cap regulation are: Braeutigam and Panzar (1989), Brennan (1989), Brown, Einhorn and Vogelsang (1989), Cabral and Riordan (1989), Lewis and Sappington (1989), Schmalensee (1989), Isaac (1991), Sappington and Sibley (1992), Laffont and Tirole (1993), and Gasmi, Ivaldi, and Laffont (1994). l0 In practice, the X-factor does not always reflect realized or anticipated productivity gains.…”