A proxy firm is a company hired by corporate shareholders to cast proxy statement votes on their behalf. The top two proxy firms are Glass, Lewis & Co. and RiskMetrics/Institutional Shareholder Services.[1] By some accounts, RiskMetrics ISS advised half of the common stock in the world as of 2010.[2] Some proxy firms play the role of proxy advisor, in which they simply advise their clients on how to vote.[3] A potential conflict of interest identified by the Government Accountability Office is that some owners of proxy firms do business with both issuers and investors.[4] In many cases, proxy firms have attempted to limit executive compensation.[5]