The S&P 500 is closing out the week at new all-time highs, but the number of stocks participating during the current run-up has been much lower than levels seen during prior breakouts this year. Below is a chart highlighting the percentage of stocks in the S&P 500 closing above their 50-day moving averages on a daily basis since the start of the year. As shown, 70% of the stocks in the index are currently above their 50-day moving averages, which is well below the breadth levels seen as recently as October when the index experienced its last big breakout to new highs. Throughout the year, we've seen breadth decline with each successive breakout, so it has definitely become more of a "stock-picker's market" late in the year. Underperforming investors trying to play catch-up with this market into year-end are likely finding it difficult.