The problem is you are not the only one knowing that earnings are coming. Everyone knows that some stocks move a lot after earnings, and everyone bids those options. Following the laws of supply and demand, those options become very expensive before earnings. The IV (Implied Volatility) jumps to the roof. The next day the IV crashes to the normal levels and the options trade much cheaper.
Over time the options tend to overprice the potential move. Those options experience huge volatility drop the day after the earnings are announced. In many cases, this drop erases most of the gains, even if the stock had a substantial move. In order to profit from the trade when you hold through earnings, you need the stock not only to move, but to move more than the options "predicted". If they don't, the IV collapse will cause significant losses.
However, there are always exceptions. Stocks like NFLX, AMZN, GOOG tend on average to move more than the options imply before earnings. It doesn't happen every cycle. Few cycles ago NFLX options implied 13% move while the stock moved "only" 8%. A straddle held through earnings would lose 32%. A strangle would lose even more. But on average, NFLX options move more than expected most of the time, unlike most other stocks.
NFLX reported earnings on Monday October 17. The options prices as indicated by a weekly straddle "predicted" ~$10 (or 10%) move. The $100 calls were trading at $5 and the puts are trading at $5. This tells us that the market makers are expecting a 10% range in the stock post earnings. In reality, the stock moved $19. Whoever bought the straddle could book a solid 90% gain.
Implied Volatility collapsed from 130% to 36%. Many options "gurus" advocate selling options on high flying stocks like NFLX or AMZN, based "high IV percentile" and predicted volatility collapse. However, looking at history of NFLX post-earnings moves, this doesn't seem like a smart move.
As you can see from the table (courtesy of optionslam.com), NFLX moved more than expected in 7 out of 10 last cycles. For this particular stock, options sellers definitely don't have an edge, despite volatility collapse. If the stock moves more than "expected", volatility collapse is not enough to make options sellers profitable.
Generally speaking, I'm not against selling options before earnings - on the contrary. For many stocks, options consistently overestimate the expected move, and for those stocks, this strategy might have an edge (assuming proper position sizing). But NFLX is one of the worst stocks to use for this strategy, considering its earnings history.
If you want to learn how to trade earnings the right way (we just booked 26% gain in NFLX pre-earnings trade):
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