The independence of editorial content from advertisers’ influence is a cornerstone of journalistic ethics. Jonathan Reuter and Eric Zitzewitz tested whether this independence is observed in practice. They found that mutual fund recommendations are correlated with past advertising in three personal finance publications but not in two national newspapers.

Their tests controlled for numerous fund characteristics, total advertising expenditures, and past mentions. While positive mentions significantly increase fund inflows, they do not successfully predict returns.

The magazine publications they looked at were Kiplinger’s Personal Finance, Money Magazine and Smart Money. And the national newspapers were the Wall Street Journal and the New York Times.