January barometer or January effect is a theory which states that the equity market performance during the month of January will set the tone for the rest of the year. In other words, a negative return in January, according to the theory, would imply a bearish year while a positive performance should indicate a financial year characterized by an uptrend. The equity indices that will be examined in the current research are S&P500, NASDAQ Composite, DAX30, FTSE100, Nikkei225, ASX200, Hang Seng, Bovespa and BSE Sensex. The aforementioned indices have been selected because the aim of the current research is to test the validity of such theory across the globe and that is why we are going to look at how North and South American, European and Asian indices performed across a period of time which spans 11 years. This research was published on the Medium platform a few years ago but it is still valid today. Please click here to read the rest of the research.