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Welcome to this week's installment of "The Short Interest Report" - The Fly's weekly recap of short interest trends among some of the most widely followed high-short-float stocks. Using the data from our partner Ortex.com, which utilizes the latest information from stock lenders to estimate short interest changes for thousands of publicly traded companies, this report will screen for some of biggest changes in short interest as a percentage of free float and days-to-cover ratios while also considering the short interest data on some of the more volatile and heavier-traded names of the week. Based on the availability of data from Ortex, the report tracks the trading period that covers prior Friday through Thursday of this week, excluding holidays. As a basis of comparison for stocks discussed below, the S&P 500 index was down 3.9%, the Nasdaq Composite was down 5.0%, the Russell 2000 index was down 4.5%, the Russell 2000 Growth ETF (IWO) was down 4.9%, and the Russell 2000 Value ETF (IWN) was down 4.2% in the five-day trading session range through Thursday, September 21st.

SHORT INTEREST GAINERS

• Ortex-reported short interest in EVgo (EVGO) matched its lowest level of 2023 in the final week of August just below 18%, but has now been rising for four consecutive weeks. This week, EVgo short position as a percentage of free float rose to 22.5% from 21.0%, the highest level in three months. Days to cover on the name was up 130 basis points to 8.2, also the highest level in three months. Last week, we profiled EVgo peer Blink Charging (BLNK), whose shares had also seen a steady buildup in short positioning. This week, Blink Charging shorts as a percentage of free float exceeded the also continued to build, reaching a seven-month high above 29%. In the five-day period covered, shares of EVgo were down 10% and those of Blink Charging fell 21%.
• Ortex-reported short interest on Virgin Galactic (SPCE) slipped to a one-month low of 17.9% late last week, but with the stock sliding to fresh multi-year lows, bears are once again building their positions. Shorts as a percentage of free float rose to 20.7% this week, the highest level since August 4 despite the ongoing momentum in commercial near-space aviation as the company has announced that 'Galactic 04' flight window – its fifth space flight this year - will open on October 5. With trading volumes down this week from last Friday's spike, days to cover on Virgin Galactic was up 200 basis points to 6.0 – a three-month high. For the week ended Thursday, shares of Virgin Galactic were down 8.5%.
• Estimated short interest on Petco Health (WOOF) rose another three percentage points this week to 22.5% - the highest level for the stock since early January. The increase marked the second consecutive week of outsized gains as last week's short interest change was to the tune of four percentage points from a 17-month low of 15.5%. Prior to the rise in bearish bets, shorts had taken their profits as the stock fell sharply in late August after the company's FY23 earnings guidance was cut due to a "shift in consumer spending", though bears are now betting on more structural pain for Petco, with Walmart announcing the opening of its first pet services store this week. Shares of Petco were down 18.1% this week and have now lost over 60% from mid-July highs.

SHORT INTEREST DECLINERS

• Estimated short interest in Marathon Digital (MARA) declined from 27.0% to 25.1% while days to cover on the stock was down by 30bps to 1.8. Short positioning on the stock has trended within a 21.5%-27.5% range over a six-month period and without much directional bias despite the more pronounced volatility in the stock and the broader cryptocurrency asset class. This week, shorts as a percentage of free float merely retreated from the upper band of that range, while the stock slipped 8.4%, even with the price of bitcoin breaking out to 3-week highs above 27,000.
• Ortex-reported short interest in C3.ai (AI) matched a two-month high of 36.3% early last week but saw a pullback this week as bears took some profits. Shorts as a percentage of free float was down from 35.8% to 33.8% while the stock fell 9.1% in the five-day period covered. C3.ai shares are still in a tailspin following the company's Q1 results and affirmed FY24 guidance, down 18% from pre-earnings levels and down nearly 50% from this year's mid-June highs.