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The Mid-Month Payday Anomaly in the S&P 500

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Summary

The document describes a calendar effect attributed to semi-monthly paychecks. Its proposed explanation is that employees receive wages around the 15th and some retirement contributions arrive at financial institutions for investment the following day. The strategy takes a long position in the S&P 500 only on the 16th of each month, using publicly available market data.

The cited study reports that the 16th ranks among the strongest calendar days, behind only the 1st and 2nd, and that its ranking improved across decades through the 2010s. This is evidence of an observed historical pattern, not proof that paycheck flows cause it or that it will persist. The document also notes that more employers are moving to bi-weekly pay schedules, which may weaken the effect. Because the position is long-only equity exposure, it is not presented as a bear-market hedge or crisis diversifier.

Key ideas

  • The strategy holds the S&P 500 on the 16th calendar day of each month.
  • The proposed mechanism is investment of retirement contributions after semi-monthly paydays.
  • The cited research finds the 16th among the strongest return days, behind the 1st and 2nd.
  • The observed pattern may weaken as payroll schedules shift toward bi-weekly payments.
  • The long-only equity exposure does not provide a hedge during market crises.

Tags

EquitiesEvent-drivenBacktesting

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.