Author Correction: Empirical evaluation of the stringency and design of renewable portfolio standards

In the version of this Article originally published, there was a data entry error in Table 1 for a single variable, eligibility of non-renewable resources in a renewable portfolio standard. This affected the descriptive statistics in Table 1 and Fig. 4 and the regression results and efficiency variable in Table 2. It also affects parts of the text, Table 3 and the Supplementary Information. These corrections have now been made.