Efficient Capital Markets: Il TORIo Eugene f fama The Journal of finance, Vol. 46, No. 5. (Dec, 1991), pp. 1575-1617 Stable url: http://inks.jstor.org/sici?sici=0022-1082%028199112%02946%3a5%3c1575%3aecmi%3e2.0.co%3b2-l The Journal of finance is currently published by American Finance Association Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/about/terms.htmlJstOr'sTermsandConditionsofUseprovidesinpartthatunlessyou have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://wwwjstor.org/journals/afina.html Each copy of any part of a jSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission jStOR is an independent not-for-profit organization dedicated to creating and preserving a digital archive of scholarly journals. For more information regarding JSTOR, please contact support@jstor. org http://www.jstor.org/ Tue Apr2513:07:272006