This idea is similar to "Sell in May and go away" or "Halloween effect."
From 1950 to around 2013, the Dow Jones Industrial Average has had an average return of only 0.3% during the May to October period, compared with an average gain of 7.5% during the November to April period, according to a 2017 column in Forbes. While the exact reasons for this seasonal trading pattern were not known, lower trading volumes due to the summer vacation months and increased investment flows during the winter months were cited as contributory reasons for the discrepancy in performance between the May to October and the November to April periods.
However, recent statistics suggest that this seasonal pattern may not be the case anymore. According to a May 2018 article in Investor's Business Daily, if an investor had sold stock in May 2016, she would have missed some lucrative runs. The NASDAQ ended April 2016 at 4775.36; it closed higher in May and soared in late June. The NASDAQ rose by 55% from the end of June 2016 until the end of January 2018.
https://www.investopedia.com/terms/s/sell-in-may-and-go-away.aspI think the reason for such an anomaly is trading activity. If the majority of traders out for vacation, it is understandable if the trading activity will decline, along with the price. However, don't forget that in this modern era, traders still can use their smartphone anywhere to do some trading activity. Also, not all of us are Chinese and would ignore the Chinese New Year.
