NBC was scheduled to make a major presentation to advertisers today (Thursday) to try to convince them that their notions that older viewers spend significantly less money than younger ones. As reported by MediaWeek magazine, NBC research head Allen Wurtzel, previewing the presentation to reporters on Wednesday, said that the adult 55-64 demo "is the fastest-growing demo group in the country and now numbers 35 million people that account for close to $2 trillion in annual spending." He insisted that advertisers' age-demo data "were invented 50 years ago and are outdated." Wurtzel said that NBC's own research ought to cause advertisers who ordinarily spurn programs that attract older viewers -- particularly nightly newscasts -- to reappraise their thinking. The research, for Example, shows that people in the 55-64 demo spend more on home-improvement products than those in the 18-49 demo. "Maybe," he said, "home improvement chains should be advertising on the nightly news."