Since the pioneering work of Harry Markowitz in the 1950s, sophisticated statistical and mathematical techniques have increasingly made their way into finance and investment management. One might question whether all this mathematics is justified, given the present state of economics as a science. However, a number of laws of economics and finance theory with a bearing on investment management can be considered empirically well established and scientifically sound. This knowledge can be expressed only in the language of statistics and mathematics. As a result, practitioners must now be familiar with a vast body of statistical and mathematical techniques.