The empirical legal study of tax law has developed greatly in recent years and has yielded many insights into the judiciary in particular and the legal system as a whole. This article continues this process by evaluating, through the prism of tax litigation and based on theories of analyzing judicial decision making, the effect of law reforms on win rates and whether win rates can help predict future law reforms. The analysis is based on a comprehensive database (census, not sample) of 1,330 tax decisions of the Israeli Supreme Court (ISC), divided into seven tax categories, and covering 60 years of tax jurisprudence since Israel's establishment (1948–2008). The data enabled us to find changes in win rates over time, among different tax categories, and in relation to several tax reforms. The detailed analysis found that law reforms have a significant effect on win rates and that win rates have a predictive ability for future law reform. These findings strengthen the legal model and the neo-institutional theory and do not provide support for selection effect theory or the attitudinal model regarding their explanatory function in analyzing judicial decisions.