Whether the source of information was self-reported by the companies, or provided through independent external evaluation, could result in different outcomes as discussed below. Second, the construction of a single weighted index for social performance was methodically questionable (Rowley and Berman, 2000; Margolis and Walsh, 2001). For example, it is debatable whether such weighted index which was aggregated along different dimensions for different industries can be compared (Rowley and Berman, 2000). Those two issues are investigated below. With regard to the first issue, of data sources for measuring social responsibility, four practices existed (Margolis and Walsh, 2001):