Here is a compiled review of the most significant insider trading activity reported in U.S. equity markets on Monday, covering transactions executed between May 14 and May 18, 2026. The disclosures show a blend of large-scale purchases by prominent investors and strategic disposals by corporate executives.
Top buys
Republic Services, Inc. (RSG) registered the single largest insider purchase disclosed during the period. William H. Gates III and Cascade Investment, L.L.C. together acquired a total of 486,000 shares of Republic Services for approximately $101.8 million. The purchases were executed over several days, from May 14 to May 18, 2026, and consisted of multiple transactions. Reported trade prices ranged from $206.03 to $215.46 per share; each reported figure represents the weighted-average price per share for those transactions.
Republic Services operates in the Commercial Services & Supplies industry and carries a market capitalization of $66 billion. At the time of the filings, the stock was trading above its fair value as assessed by market analysis referenced in the filings. The company posts a price-to-earnings ratio of 30.85 and has a 24-year record of consecutive dividend payments, with a current yield of 1.17%.
PAR Technology Corp (PAR) drew significant attention from Voss Capital, LP and affiliated entities, which collectively purchased common stock valued in excess of $10.5 million. These acquisitions occurred on May 14 and May 15, 2026, and involved 719,800 shares purchased at prices ranging between $14.4987 and $14.6712 per share. Several entities in the Voss group participated in the transactions; together they form a group of beneficial owners holding more than 10% of PAR’s outstanding common stock.
The timing of this buying activity is notable given PAR Technology’s recent share-price performance. Over the past year the stock has tumbled nearly 80%, trading near $14 versus a 52-week high of $72.15. Market commentary included in the disclosures indicates that the shares appear undervalued at current levels, with analyst price targets reported in the filings ranging from $18 to $45.
Bakkt, Inc. (BKKT) reported a sizable insider purchase by director Michael Alfred, who acquired 585,000 shares of Class A Common Stock for a combined value of roughly $4,848,100. Those acquisitions occurred on May 15 and May 18, 2026, with per-share prices ranging from $8.20 to $8.34. On May 15 specifically, Mr. Alfred bought 365,000 shares at a weighted-average price of $8.34 per share through multiple trades, with individual trade prices spanning $7.91 to $8.63.
Bakkt’s shares have shown substantial volatility recently. The filings note a 12% decline in the last week and a 49% drop over the prior six months.
Lifeway Foods, Inc. (LWAY) saw Divisadero Street Partners, L.P. and Divisadero Street Capital Management, LP expand their holdings by purchasing common stock amounting to approximately $4,200,968. The transactions took place on May 14 and May 15, 2026, with executed prices ranging from $22.9794 to $26.3251 per share. On May 14, Divisadero Street purchased a total of 131,871 shares across three separate trades, including 95,371 shares at a weighted average price of $25.2365 per share, where individual prices ranged from $25.1592 to $25.4584. Additional lots included a 1,500-share block at $22.9794 and a 35,000-share block at $26.3251.
Lifeway Foods trades with a market capitalization of $365 million and, according to the filings, has shown momentum with revenue growth approaching 22% over the last 12 months.
Shake Shack Inc. (SHAK) disclosed that director Daniel Harris Meyer increased his ownership stake by acquiring 32,258 shares of Class A Common Stock valued at roughly $1,996,215. Reported on May 15, 2026, the shares were purchased by the Daniel H. Meyer Investment Trust at a weighted average price of $61.8828 per share, with individual trades priced between $61.63 and $62.00. Following the purchases, the Investment Trust holds 378,670 shares of Shake Shack Class A stock.
These purchases were reported as occurring while the stock trades near its 52-week low of $59.93, with the shares down 49% over the prior 12 months. The filings include commentary that the stock appears undervalued at current levels.
Top sells
Innodata (INOD) disclosed a mix of sales and option exercises by Chief Executive Officer Jack Abuhoff. Across transactions on May 15 and May 18, 2026, Mr. Abuhoff sold a total of 250,000 shares for an aggregate of about $23.7 million. Concurrently, he acquired 250,000 shares via the exercise of stock options.
On May 15, the filings detail that Abuhoff sold three lots: 14,041 shares at a weighted average price of $94.88 per share, 76,142 shares at a weighted average price of $95.87 per share, and 9,817 shares at a weighted average price of $96.36 per share. The total for those sales was reported at approximately $9,557,178. In parallel, he exercised options to purchase 100,000 shares at $4.99 per share, totaling $499,000. The filings note that the exercised options were fully vested and exercisable as of January 1, 2025.
Innodata’s shares have performed strongly, delivering a 162% return over the past year and trading at $94.69, placing the company at an estimated market capitalization of $3.06 billion. Market commentary in the disclosures describes the stock as trading well above its fair value.
StoneX Group Inc. (SNEX) reported that Chief Financial Officer William J. Dunaway sold 64,017 shares of common stock on May 15, 2026. The disposal generated proceeds of approximately $7,071,208, with the shares sold at an average price of $110.4583 per share.
United Therapeutics Corp (UTHR) disclosed that Chairperson and Chief Executive Officer Martine A. Rothblatt sold 9,500 shares of common stock on May 15, 2026, receiving roughly $5,397,077. The sale was executed at prices spanning $566.1876 to $572.2538 per share. On the same day, under the filings, Ms. Rothblatt also exercised options to acquire 9,500 shares at $146.03 per share, totaling $1,387,285.
Both the acquisition via option exercise and the subsequent sale were carried out pursuant to a pre-arranged 10b5-1 trading plan adopted November 7, 2025. That plan is set to remain in effect until the earlier of the exercise of 1,734,410 stock options - which all expire on March 17, 2027 - or December 31, 2026. The stock traded near its 52-week high of $609.35 and had returned about 86% over the previous 12 months. The filings describe the shares as appearing overvalued relative to their fair value.
Ambiq Micro, Inc. (AMBQ) disclosed two significant insider sales by senior executives. Chief Executive Officer Esaka Fumihide sold 60,000 shares for proceeds reported at $4,201,122 on May 14, 2026, following the exercise of stock options. The weight-averaged sale price was reported at $70.0187 per share, with individual trades executed within a range of $70.00 to $70.45.
On May 15, 2026, President and Chief Operating Officer Sean Chihhsiang Chen sold common stock totaling approximately $3,947,280. Those sales comprised 55,685 shares in two separate transactions: 32,351 shares sold at a weighted average price of $70.5334 per share, with individual trade prices from $70.02 to $71.0097, and 23,334 shares sold at a weighted average price of $71.3746 per share, with individual trade prices ranging from $71.025 to $71.85.
Ambiq Micro’s shares were reported trading near a 52-week high of $73.72 and showed a 206% increase over the prior six months. The filings indicate the stock appears overvalued compared with fair-value estimates, and the company carries a market capitalization of $1.51 billion.
Context and what the activity signals
Insider transactions can provide useful, though not definitive, context about how company executives, directors and large shareholders view their firms. Purchases by insiders - such as the substantial acquisition of Republic Services stock by William H. Gates III and Cascade Investment, or the coordinated buys by Voss Capital in PAR Technology - are often interpreted as expressions of confidence in a company’s prospects.
Conversely, disposals by executives - including the sales reported by Innodata’s CEO, StoneX’s CFO, United Therapeutics’ chair and CEO, and top executives at Ambiq Micro - can reflect a range of motivations. Filings in this round of disclosures explicitly note that some sales followed option exercises or were conducted under pre-arranged 10b5-1 trading plans. Insiders sell for many reasons beyond their view of a company’s near-term fundamentals, including portfolio rebalancing, personal financial planning or liquidity needs.
How market metrics in the filings relate to the trades
- Republic Services - trades above reported fair value, but attracted a large block purchase totaling roughly $101.8 million; long dividend history and a P/E of 30.85 are noted.
- PAR Technology - sizable insider buying occurred while the stock sits near an 80% decline from its 52-week high and is characterized in the filings as appearing undervalued, with analyst targets in filings ranging from $18 to $45.
- Bakkt, Lifeway Foods and Shake Shack - insiders increased positions amid share-price weakness or in the case of Lifeway, reported revenue momentum; Bakkt has shown recent volatility and Shake Shack trades near its 52-week low.
- Innodata, StoneX, United Therapeutics and Ambiq Micro - executive sales were disclosed, some tied to option exercises or 10b5-1 plans; Innodata and United Therapeutics are specifically reported as trading above or near extended valuation ranges.
Key points
- Significant insider buys were led by William H. Gates III and Cascade Investment buying 486,000 shares of Republic Services for about $101.8 million between May 14 and May 18, 2026.
- Voss Capital and affiliated entities purchased 719,800 shares of PAR Technology for more than $10.5 million on May 14-15, 2026, at prices near $14.50 per share, while PAR’s stock has fallen nearly 80% over the past year.
- Major executive sales included Innodata’s CEO selling 250,000 shares for roughly $23.7 million and Ambiq Micro’s top executives selling large blocks while the stock trades near multi-month highs.
Risks and uncertainties
- Insider sales can reflect non-fundamental motivations - such as tax or personal liquidity needs - which means sales should not be taken as direct signals of deteriorating business fundamentals for the companies involved. This affects investor interpretation across sectors including technology, healthcare, industrials and consumer services.
- Valuation commentary included in the filings indicates differing views on fair value; several stocks in the disclosures are described as trading above fair value while others are characterized as undervalued. Such divergences add uncertainty for investors attempting to draw uniform conclusions from the activity.
- Market volatility in individual names is evident in the filings - with examples including PAR Technology’s steep year-over-year decline and Ambiq Micro’s dramatic six-month gain - making short-term inference from single insider transactions uncertain.
Insider transactions are one of many inputs investors may consider. While purchases may imply confidence and sales may raise questions about valuation or timing, the disclosures here underline that motivations vary and that context - such as option exercises or rule-compliant trading plans - matters when interpreting the data.
Reporting note: This report compiles the transactions disclosed in company filings between May 14 and May 18, 2026, without projecting future outcomes. The figures and descriptions above reflect the amounts, prices and dates as reported in the respective filings.