This paper proposes graphical methods to determine whether commodity tax changes are socially improving, in the sense of improving social welfare or decreasing poverty for large classes of social welfare and poverty indices. It also derives estimators of critical poverty lines and economic efficiency ratios which can be used to characterize socially improving tax reforms. The statistical properties of the various estimators are derived in order to make the method implementable using survey data. The methodology is illustrated using a recently proposed reform of the Mexican Valued Added Tax system.