The Russell 2000 small cap index has been a prevalent lagger throughout the whole US equity rally into all-time highs. This is of concern for the health of the economy and the health of the S&P 500 index. The small-cap sector reacts the most to economic conditions and monetary policy, being the most affected if they cannot make new highs and are over 8.5% away from all-time highs we can infer that a stronger correction of 8-10% may occur in the S&P 500.
The S&P 500 is full of companies that have been artificially inflated by stock buy-backs and also monetary policy allowing for cheaper borrowing. There is a healthy retrace coming out to catch down to small caps since they have not relished in the strong economic conditions. Which presents another concern, is the economy that strong to begin with? If there is a correction, there could be more buyers in both the S&P 500 and Russell 2000 companies to help markets reach all-time highs yet again.