TY - JOUR AU - Lehmann,Bruce N. AU - Modest,David M. TI - The Empirical Foundations of the Arbitrage Pricing Theory II: The Optimal Construction of Basis Portfolios JF - National Bureau of Economic Research Working Paper Series VL - No. 1726 PY - 1985 Y2 - October 1985 UR - http://www.nber.org/papers/w1726 L1 - http://www.nber.org/papers/w1726.pdf N1 - Author contact info: Bruce Lehmann University of California, San Diego IR/PS 1415 Robinson Building Complex La Jolla, CA 92093-0519 Tel: 858/534-0945 Fax: 858/534-3939 E-Mail: blehmann@ucsd.edu AB - The Arbitrage Pricing Theory (APT) of Ross (1976) presumes that a factor model describes security returns. In this paper, we provide a comprehensive examination of the merits of various strategies for constructing basis portfolios that are, in principle, highly correlated with the common factors affecting security returns. Three main conclusions emerge from our study. First, increasing the number of securities included in the analysis dramatically improves basis portfolio performance. Our results indicate that factor models involving 750 securities provide markedly superior performance to those involving 30 or 250 securities. Second, comparatively efficient estimation procedures such as maximum likelihood and restricted maximum likelihood factor analysis(which imposes the APT mean restriction) significantly outperform the less efficient instrumental variables and principal components procedures that have been proposed in the literature. Third, a variant of the usual Fame-MacBeth portfolio formation procedure, which we call the minimum idiosyncratic risk portfolio formation procedure, outperformed the Fama-MacBeth procedure and proved equal toor better than more expensive quadratic programming procedures. ER -