A good example of the importance of considering mental accounting while crafting public policy is demonstrated by authors Justine Hastings and Jesse Shapiro in their analysis of the SNAP (Supplemental Nutritional Assistance Program). They "argue that these findings are not consistent with households treating SNAP funds as fungible with non-SNAP funds, and we support this claim with formal tests of fungibility that allow different households to have different consumption functions" Put differently, their data supports Thaler's (and the concept of mental accounting's) claim that the principle of fungibility is often violated in practice. Furthermore, they find SNAP to be very effective, calculating a marginal propensity to consume SNAP-eligible food (MPCF) out of benefits received by SNAP of 0.5 to 0.6. This is much higher than the MPCF out of cash transfers, which is usually around 0.1. Clearly, mental accounting is leveraged by SNAP to make it a more effective policy.