Why do two borrowers who appear nearly identical in credit score and income level receive significantly different annual percentage rates (APRs) when applying for a credit card at the same bank? In a study published on November 4, 2026, on Liberty Street Economics, the blog of the Federal Reserve Bank of New York, Kyle Herkenhoff, a consultant at the Federal Reserve Bank of Minneapolis, and Juan M. Morelli, a research economist in the Research and Statistics Group of the Federal Reserve Bank of New York, provide a mechanistic explanation: credit card issuers pass through changes in funding costs to a lesser extent in segmented markets where they hold a larger market share.
Understanding this conclusion requires an understanding of the structure of the credit card market. Issuers do not compete in a single, undifferentiated national market; rather, they design products and pricing strategies targeting specific types of borrowers. Industry reports, regulatory guidance, and academic research all document market segmentation based on credit risk, income levels, card characteristics, and acquisition channels. A prime borrower applying online for a standard non-co-branded card belongs to a completely different market than a subprime borrower accepting a pre-approved offer for a co-branded card. The same issuer can dominate one such segment while holding a very small share in another.
Guided by this framework, Herkenhoff and Morelli divided the national market into 960 distinct segments, combining four credit-score groups, card and product types, acquisition channels, and income groups based on the borrower’s ZIP code. In their dataset, an issuer operates in approximately 200 of these markets on average per week. Within each market, the issuer’s share is defined as its revenue relative to total revenue in that market.
They first utilized confidential account-level data collected by the Office of the Comptroller of the Currency (OCC), a U.S. banking regulator, to observe the relationship between interest rates and market share. After finely grouping accounts by characteristics such as income, credit score, and card type, they found a positive correlation of 54% between the average APR within each group and the average market share of the issuing lender within that group. This means that among borrowers with similar characteristics, cards issued by lenders with higher market shares carry higher interest rates.
However, correlation does not imply causation. High-share markets may differ in unobserved dimensions that also affect rates. To obtain more direct evidence, the authors turned to a natural experiment: when an issuer’s funding costs undergo an exogenous change, do its pricing adjustments differ between high-share and low-share markets?
The analysis focused on January 2008, which saw one of the largest unexpected drops in the federal funds rate (25 basis points). For new accounts, issuers set the initial APR and its spread over the benchmark rate at origination. The authors compared cards issued shortly before and after this unexpected rate change by the same issuer, stripping out market-wide common rate movements and controlling for observable differences in borrower credit scores, income, and card types. What remained was the difference in pass-through between high-share and low-share markets for the same issuer under the same exogenous shock.