In our daily life, almost every family owns a portfolio of assets. This
portfolio could contain real assets such as a car, or a house, as well
as financial assets such as stocks, bonds or futures. Portfolio theory
deals with how to form a satisfied portfolio among an enormous number of
assets. Originally proposed by H. Markowtiz in 1952, the mean-variance
methodology for portfolio optimization has been central to the research
activities in this area and has served as a basis for the development of
modem financial theory during the past four decades. Follow-on work with
this approach has born much fruit for this field of study. Among all
those research fruits, the most important is the capital asset pricing
model (CAPM) proposed by Sharpe in 1964. This model greatly simplifies
the input for portfolio selection and makes the mean-variance
methodology into a practical application. Consequently, lots of models
were proposed to price the capital assets. In this book, some of the
most important progresses in portfolio theory are surveyed and a few new
models for portfolio selection are presented. Models for asset pricing
are illustrated and the empirical tests of CAPM for China's stock
markets are made. The first chapter surveys ideas and principles of
modeling the investment decision process of economic agents. It starts
with the Markowitz criteria of formulating return and risk as mean and
variance and then looks into other related criteria which are based on
probability assumptions on future prices of securities.