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Sell in May and go away is an investment strategy for stocks based on a theory (sometimes known as the Halloween indicator) that the period from November to April inclusive has significantly stronger growth on average than the other months. In such strategies, stocks are sold at the start of May and the proceeds held in cash (e.g. a money market fund); stocks are bought again in the autumn, typically around Halloween. "Sell in May" can be characterised as the belief that it is better to avoid holding stock during the summer period. Though this seasonality is often mentioned informally, it has largely been ignored in academic circles (perhaps being assumed to be a mere superstition). Nonetheless analysis by Bouman and Jacobsen (2002) shows that the effect has indeed occurred in 36 out of 37 countries examined, and since the 17th century (1694) in the United Kingdom; it is strongest in Europe. While the effect may reflect a failure of the efficient-market hypothesis, alternatives exist such as small sample size or time variation in expected stock market returns. ==Cause of the effect== Although it's not clear what causes the effect, what's most interesting is that it shows that stock market returns in many countries during the period May–October are systematically negative or lower than the short-term interest rate, which also goes against the efficient-market hypothesis. Stock market returns should not be predictably lower than the short-term interest rate (risk free rate). Popular media often refer to this market wisdom in the month of May, claiming that in the six months to come things will be different and the pattern will not show. However, as the effect has been strongly present in most developed markets (including the United States, Canada, Japan, the United Kingdom and most European countries) in the last decade - especially May–October 2009 - these claims are often proved wrong. That said, between April 30 and October 30, 2009, the FTSE 100 gained 20% (from 4,189.59 to 5,044.55) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sell in May」の詳細全文を読む スポンサード リンク
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