Several cross country studies find that rising household income leads to consumption spending being spread more evenly across different spending categories (Clements et al., 2006). We argue that this result is likely due to aggregation. Using more disaggregated UK household level spending data, we show that the spending diversity of households only rises up to a certain income level and then starts to decline as households concentrate more of their spending on particular expenditure categories that differ across households.

I study the effect of task difficulty on workers’ effort and compare it to the effect of monetary rewards in a tightly controlled laboratory experiment. I find that task difficulty has an inverse-U effect on effort, and that this effect is quantitatively large when compared to the effect of conditional rewards. Difficulty acts as an important mediator of monetary rewards: they are most effective at the medium level of difficulty.