Note: Most AM stations utilizing IBOC do not utilize the system at night. According to IBOC proponents, as of October 2007, "fewer than 100 stations" are utilizing the system because of skywave adjacent-channel interference problems (see "DROPPING LIKE FLIES," this site.) An unknown number of AM stations using IBOC are "daytimers" meaning they have no nighttime authority under any circumstances, or are "daytimers with post-sunset authority" meaning they have very small nighttime operating power. Since IBOC utilizes only about 1/100th of AM carrier power the system would not work reliably with the usual PSSA authorized station, operating with only 5 to 50 watts, so daytimers are not candidates for nighttime use of the system.
RELEVANT STATISTICS: 95% of AM stations do NOT operate IBOC, with something between 98% and 99% of AM stations NOT operating with the system at night. Only 84% of FM stations are utilizing IBOC, including noncommercial licensees. This is after four years of frantic industry promotion, ineffectual on-air promotion and lobbying of the FCC to establish IBOC as "the" digital standard.