helf registration for primary securities (Rule 415) began in March 1982 and S was permanently adopted by the Securities and Exchange Commission for large firms in November 1983.' Rule 415 allows a company to register all of the securities it plans to issue over the next two years and then to sell some or all of the securities whenever it desires. The rule thus simplifies the registration of new securities and allows more flexibility in the way they are sold. ' When an eligible firm decides to raise new capital, it registers the securities under Rule 415. Once the registration is declared effective, the firm can issue the securities almost instantly at any time over the next two years. If the securities are not issued by the end of the two year period, it pays a fee to have them "deregistered." To date, however, no shelf-registered securities have remained on the shelf during the entire two year period following registration. Under the new shelf registration plan, a firm can register securities and immediately issue them. The firm need not specify the coupon, maturity, or likely issue date on the registration form. At any time during the upcoming two year period, it can issue any or all of the amount registered. The advantages appear to be related to the flexibility of modifying the issue at no cost. Another important benefit of shelf registration is that the issuer increases the liklihood of finding the highest price an underwriter would pay. This effect results because once the securities are registered, the information is made public, and thus more closely approximates a competitive environment than does the traditional underwritten offering.A recent study by Kidwell, Marr, and Thompson (1984) revealed that bond issues offered under shelf registration sell for 30 to 40 basis points less than comparable negotiated sales and about 26 basis points less than competitive bid issues. The and medium size firms were excluded.