In 1885, the largest churches in Scotland were engaged in a dispute about state funding. We use data generated in the course of that dispute to test two related hypotheses. First, as market size (proxied by population) increases, the competitiveness (or complexity) of the religious market structure will not decrease. Second, religious activity, as measured by giving per member, church income and participation, will not decrease as market competitiveness (or complexity) increases. Empirical evidence lends support to the first hypothesis, but casts doubt on the second, and the supply-side theories underpinning it, which posit a causal link between increased competitiveness (complexity) and higher levels of religious activity. In interpreting the results the importance of a rich understanding of institutional arrangements—particularly market structure, governance and financing—is underlined.competition, institutional structure, Presbyterian, Scotland,