A few studies have examined the importance of the type of reward on influencing healthy behaviors. These studies have compared the influence of cash incentives with use of gift certificates. Cash incentives consistently resulted in higher rates of simple wellness behaviors than did gift certificates, though gift certificates were still quite effective. Malotte and colleagues, for example, found that 95% of drug users returned for reading of their tuberculosis screening when offered a $10 cash incentive, compared with 86% and 83% respectively for those receiving two different types of $10 gift certificates (one for a grocery store and the other for a bus pass or fast food). While less effective than cash, the gift certificates were still substantially more effective than providing no incentive. Only 49% of those receiving returned for the reading of their screening test when no incentive was offered. This literature is still undeveloped, and it is not known what types of gift certificates are the most effective.