Fifteen years since the publication of the original DGW study, the message still remains the same: increases in IRS enforcement can go a long way to increasing taxpayer compliance through general deterrence. However, the IRS should not rely solely on correspondence audits of enforcement. While much less expensive, these audits are not as effective as either-face-to-face audits or CI investigations. Meanwhile, the marginal effectiveness of IRS audits has declined since the 1977–1986 period and the amount of direct enforcement has simultaneously declined. In conjunction, these findings help explain why the tax gap continues to grow with time.