Today is the last trading day (LTD) of October.
The LTDs of months used to be stronger than average, but in recent years they have been weak. This is quite different from the first trading days of months which strongly out-perform the average for all days, and where the effect has strengthened in recent years.
Since 1984 the market has on average risen 0.49% on the LTD of October, with positive returns in 71% of all years, which makes it easily the strongest LTD of any month in the year.
However, as can be seen in the chart, the behaviour of the October LTD has changed markedly over time. For the 19 years from 1984 the market only fell twice on the October LTD; but in the 11 years since 2003 the market has only risen significantly on this day in four years.
The following chart shows the FTSE 100 Index returns for every October LTD since 1984.