Companies that hide their political spending from shareholders have less value on the market, according to a report released Tuesday by researchers at Harvard law and the Public Citizen consumer advocacy group. Harvard law and economics professor John Coates and Taylor Lincoln with Public Citizen’s Congress Watch division compared 80 companies in the Standard & Poor’s 500 that voluntarily disclose their electioneering activities with other S&P 500 companies in the same industry. The companies with disclosure policies had a 7.5 percent higher industry-adjusted price-to-book ratio than other firms, according to the report. The duo looked at price-to-book ratios, as opposed…