“…The performance and appropriateness of these policies for NPS pollution, however, continue to be challenged for a number of reasons-e.g., noncompliance (Malik, 1990), market power (Van Egteren and Weber, 1996), transactions costs (Stavins, 1995), uncertainty (Taff and Senjem, 1996), and trading ratios (Hoag and Hughes-Popp, 1997).…”