Public company securities that are not listed, traded or quoted on any U.S. stock exchange or the OTC markets are sometimes purchased or sold over the counter (OTC) via the grey market. Grey market securities have no market makers quoting the stock. Since grey market securities are not traded or quoted on an exchange or interdealer quotation system, investors' bids and offers are not collected in a central spot so market transparency is diminished and effective execution of orders is difficult.[22]