Consumers everywhere see and hear credit union marketing campaigns, from PenFed’s ubiquitous jingle to big stadium and Super Bowl sponsorship deals. In fact, according to a new ABA DataBank post from ABA’s Dan Brown and Robert Flock, credit unions spend more than double what comparable banks do on marketing as a percentage of net income.

But why do credit unions, which serve members from defined fields of membership, spend so much? On the ABA Banking Journal Podcast, Brown and Flock break down the legislative and regulatory history of fields of membership and how the average credit union has more than doubled its “potential membership” since new rules were finalized in 2015, using their taxpayer subsidy to fuel growth via marketing rather than lower rates and costs for their members.