The first two chapters of this thesis analyze the response of blood donors to several features of the blood market in Portugal. The first provides estimates of the blood supply elasticity using changes in a benefit scheme for regular blood donors. In Portugal, starting from 2003, the government strictly enforced the collection of medical user fees, but with regular donors receiving a waiver. Using within-county variations in the value of the benefit, measured as the user fee for a visit to the Emergency Department, I find that the benefit increases the number of donations, both unconditionally and conditional on the number of blood drives. I estimate a one euro increase in the user fee to increase blood donations by 1.8%, on average. I also estimate a negative elasticity of blood drives with respect to the user fees. This indicates that benefits and blood drives are substitutes in eliciting blood donations. The second chapter analyzes how waiting to donate blood affects donor retention. I use a panel of new blood donors, in Portugal, between 2008 and 2012. I find that higher waiting times make it less likely for first-time donors to donate again, controlling for donor and donation site-specific variables. A 10-minute increase in waiting time until triage results in a 0.6% decrease in donor retention, on average. Donors in the upper tail of the waiting time distribution are driving the effect. New donors at blood drives react more negatively than new donors at blood donor centers. The third chapter (joint with Matteo Galizzi and Raffaele Miniaci) reports experimental evidence on risk preferences measures, from two waves of a representative sample of the UK Household Longitudinal Survey. The subjects responded to three tests: two incentive-compatible lottery tests and a survey test measuring self-reported willingness to take risk. We find significant but low correlations between the responses to the three tests across time. Furthermore, we find that at least two thirds of the subjects made inconsistent choices across lottery tests, when controlling for individual-specific levels of background income. Finally, we find mixed evidence concerning the external validity of these tests.