I got access to ORATS (yay!) and finally have some historical options data to wrap my head around. I have been studying the slope of the IV curve versus DTE. For the SPY, the average curve over a year looks like this. Rather than do a curve fit, I just define "slope" as IV(40DTE) - IV(15DTE). In times when this number is > 0 (90% of the time in the last year), I find that SPY has a nice positive expectancy (duh). And vice versa. So hooray, there's something I can trade until I can't. However, here's what today's curve looks like (and for the past week or so): The hoped-for IV(40)>IV(15) condition is still in place, but what's up with that hockey stick? Is the market just saying that we'll have another few days of volatility, then cruise into the Santa Claus rally? Thanks!
Forgot to mention that the above graphs are for a 50 delta call. Similar trends would presumably hold for other deltas and probably also for puts.