There are lots of moving parts affecting stocks Thursday.
We already had issues around negative earnings growth and comparatively high valuations for both the first and second quarter.
We also had issues with the timing of the Federal Reserve's interest rate hike, with the only certainty being the market believes some type of hike is coming later this year.
Negative earnings growth with the Fed raising rates down the road is not a good combination.
On Wednesday, as we approached the end of the first quarter, we saw clear signs of rotation: The biggest decline were in sectors with the biggest gains for the year (semiconductors, biotech, solar), and the few gains were from those that had the biggest declines (energy, euro).
We have also seen a change in an important long-term trend: the strong dollar. The dollar strength has reversed as some have come to believe that the Fed's rate hikes may be put off longer—a trend which began last week and continues Thursday—and that has put a bid under commodities. Copper, for example, is up roughly 11 percent in the last week. Gold is up roughly 5 percent from its bottom a week ago.
Now we have some geopolitical risk coming into the equation, as Saudi Arabia and its allies bomb Yemen.