Just by looking at the continuously negative % drop over the historical data, there's a pattern in 2008 (The Crash)

9/15/08 9/29/08 10/7/08 10/9/08 10/15/08 10/22/08 12/1/08 −4.42 −6.98 −5.11 −7.33 −7.87 −5.69 −7.70

8/4/11 8/8/11 8/10/11 −4.31 −5.55 −4.62

8/21/15 8/24/15 −3.12 −3.57

2/2/18 2/5/18 −2.54 −4.60

For 2018 to reach 2008 state, lets see if there are more significant (>-4%) drops in 2018 for us to start freaking out.

Again this by all means is not a financial model, it is something that I put together to tell myself "Keep Calm"