Sponsorship spending by North American marketers will continue to grow in 1996, according to a report by IEG Inc., Chicago. Spending for 1996 is estimated to increase by 15% over 1995, to $5.4 billion. IEG said the growth is due to marketers and brands new to sponsorship programs, and interest in tie-ins with the Atlanta Olympics this summer. IEG estimated sports sponsorships would count for about two-thirds of the total spending, followed by pop music/entertainment tours at 10%. Philip Morris Cos. and Anheuser-Busch Cos. were listed as last year's leaders in sponsorships, each spending between $110 million and $115 million.