It's just a technical pullback based on the big run-up we had this week, ever since the coronavirus became a big deal, people have pulled back a little bit on Friday because they didn't know what was going to happen over the weekend.

Matt Maley

Whenever you get up to these levels, you just become more vulnerable, we know that valuations can stay high for extended periods of time, but it does make the market vulnerable to new negative developments and that is kind of what we are seeing this week.

You have a market that was narrow back in February and too concentrated in technology. Now it's even more so, there's a reason why this happens when the market is vulnerable, because people don't see a lot of value in the overall market, so they go into the small number of names they do see a lot of value in.