New York--Ad pages declined 5.21% in business and trade publications in the first half of 1999 compared with the same period last year, according to the recently released Business Information Network figures. The data, compiled by Competitive Media Reporting for the American Business Press, showed that ad pages for the first six months of 1999 totaled 397,334.62 compared with 419,173.25 pages for the same period in 1998. The largest decline occurred in the computer category, where pages fell 20.59% to 21,477.30 from 27,047.30 in the first half of 1998. The overall drop in ad pages seemed to accelerate in June, which showed a 7.02% decline from a year earlier. While the falloff in ad pages affects the core operations of business and trade publishers, Gordon Hughes II, ABP president, said that magazines generally account for only half of business media company revenues these days. The other half comes from trade shows, Web sites and other brand extensions, which are thriving, Mr. Hughes said.