In classical asset pricing models, perfect financial markets without frictions, especially no trading costs, are assumed and thus the diverse features of liquidity are ignored. However, considering liquidity in investment is important since liquidity affects portfolio investment performance (Holthausen, Leftwich, and Mayers (1991), Keim (2003), Lesmond, Schill, and Zhou (2004), Korajczyk and Sadka (2005)) and since it has a significant implication for portfolio diversification strategies (Domowitz and Wang (2002), Harford and Kaul (2004)). In addition, it has been shown that liquidity affects the cross-sectional differences of asset returns as a characteristic (Amihud and Mendelson (1986), Brennan and Subrahmanyam (1996), Amihud (2002)) or as a risk factor (Pastor and Stambaugh (2003), Sadka (2004), Acharya and Pederson (2005)).
The amount of research on the implication of liquidity on asset pricing at a global level is small relative to that for the US market. Rouwenhorst (1999) investigates the cross-sectional relation between asset returns and liquidity in 20 countries from emerging markets and found that small stocks or value stocks have higher average turnover than large or growth stocks, a finding he acknowledges to be hard to justify by existing liquidity theories. For 19 emerging markets, Bekaert, Harvey, and Lundblad (2003) show that the covariance of country-portfolio returns with local market liquidity predicts future returns, but they could not find evidence that global liquidity risk is priced. On the contrary, Stahel (2004b) investigates the existence of market-wide comovements of liquidity of individual stocks at the country, industry and global market level in 3 developed countries of Japan, UK and US.