Although the S&P 500 is ending the week little changed (as of this writing it is trading 7 bps higher today), yesterday's gain came in at a more impressive 86 bps. Besides the size of the move higher was that the gain occurred on very strong breadth with the S&P 500 registering an "All or Nothing Day". We consider any day an "All or Nothing Day" when the daily advance/decline line (the difference between the number of S&P 500 stocks rising and falling on a given day) comes in at above +400 or below -400. In other words, these are days when broad swathes of the market trade in the same direction.

Recently, all-or-nothing days have been hard to come by. On a rolling 200-day basis, only 4.5% of days have registered such readings. Following very elevated readings just one year ago, current levels are now down around some of the lowest of the past two decades.

For this calendar year, yesterday was also the first all-or-nothing day of the year. Since 2008, when the pace of all-or-nothing days experienced a structural increase in frequency as the popularity of ETFs ballooned, the only other year where the first occurrence came later in the year was 2017 when it took 72 trading days.

Not only have "All or Nothing Days" been fairly uncommon lately, but before yesterday it had been just over three months since the last one was observed. As shown below, that is one of the longer streaks of the past couple of decades. The last streak of such a length ended in late January 2020. Of course, there have been multiple streaks that have run much longer such as 2006 and 2018 which were nearly twice as long. Or going further back to the 1990s (not pictured in the chart below), there have been streaks that have gone on upwards of 561 trading days.

In the table below, we show the performance of the S&P 500 following the end of each other streak without an all-or-nothing day since 1990 that has lasted at least three months. This most recent streak just barely made that three-month mark, but following prior streaks performance was mixed. After these streaks have ended, the S&P 500 has traded higher only a little better than half the time one week, one month, and three months later. Additionally, median returns were weaker than the norm for all periods since 1990. Six months to a year later, the S&P 500 traded higher much more consistently, albeit again median returns have trailed the norm.

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