All possible subsets of our full dataset (of at least five years duration) were taken, as well as all possible subsets of the data for each separate trap (of at least five years length, and consisting of data from at least five years to account for years when some traps were unrecorded). For each data subset, we calculated change per year in biomass in two ways: (i) as the percentage change per year predicted by a linear regression through all years of data, and (ii) as the percentage change per year between biomass in the first and last years of the data subset (to mimic studies where a particular location might only be sampled twice, with an interval of five or more years). Panels a, b show the results for the linear regression approach: a across all traps (each point represents the average across all traps for a given duration/start date combination), and b for each trap. Panels c, d show results for the first-last year analyses: c across all traps, and d for each trap. Panels e-f show the correspondence between these two types of analysis (that is, regression versus first-last date) when applied to the same duration/start date combination. The two approaches commonly agree but not always. Blue points in e-f indicate data subsets where both approaches to estimating biomass change were in agreement about the direction of change (increase or decline), and orange points highlight subsets where the methods produced different outcomes. In panels b, d, and f, points are plotted with 95% transparency to visualize density of overplotted points.