From the November issue: One of the most important names in Madison Avenue retail is not lit up in glitzy letters above a swanky boutique. But among those who know Madison Avenue’s “Gold Coast,” from 57th Street to 72nd Street — and have watched the strip suffer an uncharacteristic glut of vacancies — the low-profile Friedland family holds the informal title as the masters of Madison’s destiny. Madison Avenue has suffered the steepest rent drops of any major Manhattan retail district — the average asking rent plunged 41 percent, to $770 per square foot, in the third quarter of 2009 from the fourth quarter of 2008, according to CB Richard Ellis. If that isn’t bad enough, numerous sources said asking rents on Madison Avenue have actually plummeted even lower than the CBRE report indicated, to as low as $500 per square foot, while vacancies remain stubbornly high. One broker counted 11 availabilities, both publicly and quietly marketed spaces, just between 66th and 68th streets. Now, as the avenue’s leasing limps back to health, the Friedlands are expected to play an outsize role in its future development, tenant mix and rent levels.