In 1981, Banz discovered evidence suggesting that small-cap firms outperform large-cap firms when considering risk-adjusted returns. Banz (1981), called this the “size effect” and raised concerns regarding the ability of current asset pricing models to set accurate prices for assets. This resulted in new models being developed, such as the Fama and French three-factor model which takes the size of a company into consideration (Fama & French, 1992).

However, since the discovering of the size effect, several researchers have started to question its existence. (Asgharian & Hansson, 2008) Moreover, short after Banz findings, a study by Keim (1983) introduced results that complements the size effect. Keims study suggests that the size effect is present due to the fact that small-cap firms outperform large- cap firms during the month of January. This seasonal anomaly is called the “January effect” and could possibly be the reason for the existence of the size effect.

The purpose of this study is to investigate if there is a size effect and/or a January effect present on the Swedish stock market (OMX) when using Enterprise Value as the measure for size. Enterprise Value has been chosen in order to consider the full capital structure of companies, hence, not solely the equity value. In order to answer these research questions, a quantitative study has been conducted on companies being listen on the OMX during the time period 2000-2019. The findings of the research are that there is no size effect present on the OMX. Furthermore, the research has found that there is a January effect present on the OMX. This paper suggests that the January effect might have been the reason for the presence of the size effect in history, but as of now, the size effect has diminished but the January effect still remains.