By LARRY KANTER Staff Reporter Few would question the fact that L.A.’s show business boom has transformed the economy of the San Fernando Valley. Far less certain, however, is how the myriad television production companies in Burbank, Studio City and Sherman Oaks stack up against one another. That’s because entertainment companies tend to jealously guard their financial information. Even the production units of publicly owned entities, such as Warner Bros. and Walt Disney Co., balk at breaking out the numbers generated by their various divisions which made compiling the Business Journal’s first-ever List of television production companies a challenge. Rather than ranking the Valley’s 25 largest television production houses on the basis of revenues or number of employees, the Business Journal ranked the region’s TV producers on the number of programs currently in production. Those producing network shows were ranked highest, followed by those producing syndicated shows, followed by those producing one-time specials. The results leave no doubt that the East Valley is the center of TV production activity, with the 25 firms on the List cranking out a steady stream of shows for broadcast and cable outlets. Burbank-based Warner Bros. Television leads the tally, with 18 shows in production including such highly touted titles as “The Drew Carey Show,” “ER” and “Friends.” Following Warner Bros. on the List is NBC Television, which has 13 series in production, including “City Guys” and the award-winning “Homicide: Life on the Street.” In the No. 3 spot is Dick Clark Productions, which has 12 broadcast shows in production, including a number of award shows and a stream of “blooper” specials. Television production has become increasingly important in recent years, with four of the world’s largest entertainment companies Disney, Warner Bros., Paramount Pictures and Fox Inc. either creating or purchasing TV networks in an attempt to own both programs and a distribution channel for them. But despite the fact that many studios now own networks, independent producers are in little danger of being shut out, for this simple reason: No matter who owns the network, it has to buy the best shows to remain competitive. Networks and individual stations make most of their money on selling air time to advertisers, and ad rates are pegged to the number of viewers tuning into a particular show. So if the shows are not popular and viewers don’t tune in, the network or station can not successfully compete for advertising dollars. Some of the busiest production companies in the Valley are independents, including Studio City-based Carsey-Warner Productions, which has five shows in production, including such hit sitcoms as ABC’s “Cybill” and NBC’s “Third Rock From the Sun.” Of course, there also are plenty of firms producing more-obscure programs, most of them created for cable. No. 16 on the List, Sherman Oaks-based Weller/Grossman Productions, for example, has nine series in production, including “Curses,” Master Hoaxes,” and “Witches.” Animation also is making its mark in the Valley, with several companies including Film Roman Inc., DIC Enterprises Inc. and Ruby Spears Productions producing cartoon series for both cable and broadcast networks.