As of writing this post, the S&P is sitting at -.09% for the day, having recovered some early losses in the trading day. The Dow is even farther down, at  -.29%, and the Nasdaq 100 is actually up +.19%. 

Mixed markets are often a sign of a sector imbalance, and this is confirmed by SPDR's Sector Tracker. Materials lead the losers at -0.93%, accompanied by Consumer Staples (-0.55%), Industrials (-0.65%), Energy (-.05%), and Utilities (-0.38%). The gainers are the rest of the sectors: Communication Services (+0.36%), Financials (+0.09%), Health Care (+0.15%), Real Estate (+0.08%), and Technology (+0.13%). 

The S&P 500 is a blended benchmark, meaning it contains relatively equal weights in each sector. As a result, it reflects the average performance across all sectors. The Dow Jones, on the other hand, has a large bias toward Industrials and Materials, which explains why it is falling faster than the S&P. On the other side of the spectrum, the Nasdaq's  positive performance can be credited to its tech bias.  

So why is there a sector imbalance? I have a hypothesis: investor preference. Because the equity markets have been so incredibly bullish these past months, investors are "risk-on". This means that there is a paradigm shift away from safe, consistent stocks and into the high risk, high return baskets. This is rewarding investors now, but if markets continue to decline, it is likely we'll see the exact opposite of what we are seeing today. Investors will flee to the safety they had thrown the wind the week before.