SPY: Short interest holds near 10% as options hedging eases

Short interest in SPY has stabilised near its one-month high while options traders have quietly reduced their defensive positioning, creating an unusual divergence for the world's largest equity ETF.

Borrowed shares edged down fractionally to 101 million on October 20, equivalent to 9.84% of the free float. That is essentially flat on the week but up 24% from a month ago, continuing the build that has been in place since mid-September. The pace of that build is the more interesting data point: short interest was sitting near 82 million shares as recently as late September, so the 20-million-share addition in under a month represents a meaningful shift in how bearishly positioned the market is against the benchmark. The ORTEX short score climbed to 51.4, its highest point in the 10-day history available, having risen from 46.0 on October 8. The score is moving in the same direction as the short interest itself, reinforcing rather than contradicting it.

The borrow market tells a more nuanced story. Availability has tightened sharply over the past two weeks, dropping from above 1,500% in early October to 496% now. In absolute terms that remains comfortable, meaning lenders still hold roughly five shares available for every one out on loan. Cost to borrow has dipped back to 0.35%, having briefly spiked above 0.47% earlier in the week. Borrow is cheap and plentiful enough that there is no mechanical squeeze pressure, but the availability trend confirms that demand for borrowed shares is outpacing supply at the margin.

Options positioning has moved in the opposite direction to short interest, and that contrast is worth naming. The put/call ratio is running at 1.84, about 0.8 standard deviations below its 20-day average of 1.91. Relative to its own recent history, hedging demand via the options market is actually lighter than normal. The 52-week range for the PCR is 1.27 to 2.33, so today's reading is closer to the less-defensive end of that band. The prior stock report noted the PCR nudging slightly higher; the latest data reverses that, with Monday and Tuesday both printing below 1.85. Shorts are building in the lending market while options buyers are hedging less aggressively than they were a week ago.

On ownership, the picture is dominated by market-makers and prime brokers rather than conviction investors, which is what you would expect for an ETF of this size. Jane Street added 24 million shares in the quarter to June, the largest single-holder increase in the top 15. D. E. Shaw rebuilt a 14 million share position essentially from scratch, adding 13.3 million shares. On the other side, Morgan Stanley trimmed 8.1 million shares and Goldman Sachs reduced by 4.3 million. These are largely hedging and arbitrage flows rather than directional bets, but the concentration of big additions among market-makers at a time when short interest is rising is consistent with heightened two-way activity in the ETF.

The ETF itself closed at $769.05 on October 20, up 0.3% on the day but still 1.2% lower on the week. The one-month reading is a modest positive at 0.97%. With short interest anchored near 10% of the float and availability continuing to tighten, the question for next week is whether the short build accelerates further or plateaus as earnings season delivers its verdict on the megacap names that dominate the index's weighting.