Imbalanced numbers of men and women in societies or social groups (i.e. sex ratios) have been linked to a variety of social consequences. Studies report associations with relationship formation patterns and timing, divorce rates, fertility timing and rates, sexual norms, female labour market participation as well as violence and aggression. Theoretical arguments commonly start from a social exchange perspective, considering the sex ratio as a factor shaping individuals’ dyadic power both on the partner market and within relationships. Consequentially, behavioural consequences are theorized to result for these power and opportunity cost imbalances. However, theoretical reasoning remains unclear about whether behavioural consequences result from individuals’ deliberate adjustment of partner market strategies or unconscious endocrinal or normative variations. We fill this causal gap using longitudinal pairfam data to analyse correlations between local and perceived sex ratios in Germany. Our results show that correlation between individuals’ perception of sex ratios in daily life interactions and local sex ratios is very low. Results are robust for a variety of operationalisations for local sex ratios and essentially the same for municipality and county level. Additionally, we analyse transitions into relationships and find significant effects of local sex ratios only for women, while subjective sex ratios show significant effects. Our models show that local and perceived sex ratio effect estimates are independent, corroborating our prior finding. In sum, our findings suggest that local and subjective sex ratio are independent of one another. Consequently, sex ratio effects on behavioural outcomes are rather unlikely to be due to conscious strategy adjustments. Subjective partner availability and local sex ratios appear to be separate factors, questioning stated mechanisms of sex ratio effects on behavioural outcomes via optimizing choices. Instead, local sex ratios may affect relationship formation via processes not observed by individuals.