NEW YORK — The New York Times introduced a dagger symbol on its Best Seller list in 1995 to flag titles whose sales included bulk purchases. The change followed the release that year of "The Discipline Of Market Leaders," after it emerged that its authors had hired a book sale laundering firm to buy large quantities of copies and reach the list.

The Best Seller list is based on a weekly survey of tens of thousands of bookstores around the country, according to the paper's standard statement. The identities of the specific bookstores surveyed are not publicly disclosed, and authors speculate about the sources, weighting, and processing of the sales data used to compile the rankings.

The paper's bestseller department compiles data covering the majority of book sales in the United States and conducts extensive analysis intended to reflect the nation's literary tastes. Patrick Healy, assistant managing editor at the Times, oversees standards including the bestseller list team.

"We know that gaming does go on. People try to attempt to influence their ranking on the list, but we have a lot of steps in our process in terms of the analysis that we do with that confidential reporting from booksellers," Healy said.

"Because we want the lists to reflect organic demand, we're really focused on that rigorous application of our methodology so that our audience believes in the list, trusts in the list, comes back to the list every week," he said.

Efforts to influence the rankings predate the dagger symbol. Jacqueline Susann, who published her debut novel "Valley Of The Dolls" in 1966, used relationships with booksellers who reported to the Times to direct purchases to those retailers and boost first-week sales. Her visits to key bookstores nationwide contributed to the development of the modern book tour and generated sales, and the novel reached number one on the list. Politicians, ministers, and business leaders have since used bulk sales campaigns — through super PACs, megachurches, or hired firms — to purchase large quantities of books and secure a spot on the list.

Laura McGrath, a Temple University professor who teaches the history of bestsellers, described the impact of list placement. "What happens when a book is named to a bestseller list is a sort of rich-gets-richer effect. It has a snowball effect where being named a bestseller becomes a self-fulfilling prophecy," McGrath said.