Lists and rankings spark a split reaction from a lot of magazine readers. On the upside, they can present a lot of information in an easily digestible and often provocative form. The downside is that they tend to be reductive, at times lazy, and their profusion makes the whole concept seem a bit dull.Not so with the granddaddy of the genre, the Fortune 500, which, as it celebrates its 50th edition this year, is a reminder of how a well-researched, well-presented list attached to a credible brand can not only further that brand's reach, but actually shape the dialogue in the area it covers. As Fortune communications director Carrie Welch explains it, "Fortune is a well-known and distinguished brand about to celebrate its 75th anniversary, but the Fortune 500 is probably a better-known brand than Fortune itself." That this is the case in 2004 might have surprised its creators, who conceived the list as pretty much an afterthought. In 1955, a Fortune editor asked a secretary to compile a list of the largest industrial companies in the nation as a reference for in-house use. When it was released to readers, it caught on and has since stayed fresh by constantly evolving, adding service companies, and making other changes. In the process, it's become the benchmark for any company with major ambitions, perhaps the most familiar measure of business success in a country whose business is business, as the saying goes. "It's part of our vocabulary," Welch says. "When you say Fortune 500, you instantly get a vision of blue-chip big business." Welch and her PR team are ringing in the 50th with a lot of publicity bells and whistles that you'd expect. The magazine's bigs rang the opening bell at the New York Stock Exchange one morning last month, and there are plans for a major conference and a gala dinner. The Fortune website, too, has a number of features tied to the anniversary, from timelines to a number of different ways to support the 500 data. Though a less conspicuous part of the anniversary program, the online part is well- researched and extremely useful to anyone who wants to chart the comings and goings of the largest companies and understand, in a macroscopic way, American business. These are the same qualities that have made the Fortune 500 so lasting. Where other magazine lists rely on anecdote or the whims of editors and reporters, the 500 is the result of hard research that makes it relevant to readers. The other reason for its endurance is how relevant it is to the business community. For the corporations on it, it's vital. The story of any company's performance is told in any number of financial statistics that few take the time to read and process. So a company's presence on filters like the 500 and stock market indices like the Dow Jones is a crucial part of its public perception. Just ask Kodak or AT&T about this.