Here's a study of sorts, from last Friday pm:
The figures above stem from Open Interest on SPX options in the 350point, 71 strikes (inclusive) from 2525 to 2875. Cell BQ102 shows that Feb28 call options ITM numbered 84k, or 31% of the total for that 350 point range, while the puts (BR103) numbered 56k, or 17%.
For the six expiries covered, ITM options currently averaged 15% for puts, and 33% for calls -- or 85% OTM for puts, and 67% OTM for calls.
Would these numbers be reasonable 'ball-park' estimates for expiration status? Yes. The Open Interest numbers tend to grow or stay static; I cannot recall ever seeing OI shrink. Further, as the market rises and falls, the market's requirements for seeking/offering risk/liquidity via options would similarly march up and down the strikes --
with the actual proportions not changing all that much. {I offer that as a Straw Man supported mostly by personal observation: I've never once seen things flip.}
It is a simple procedure to test this wispy hypothesis empirically, though -- just gather OI on the front option series at 15:59 each Monday, Wednesday, Friday for a week or three, and run some sums. That's all there is to it.
(The attached .pdf has a complete snapshot of data...)
(Also, ignore BT95:BZ99 -- that data is pulled/arranged for charting)