Here are the biggest holdings of Bill Ackman, who is doubling the return of the S&P 500 this year

  • Pershing Square's investment in Chipotle buoyed Pershing's gross returns by 6.2 percent in 2018 and is up more than 38 percent year to date.
  • Another strong performer for manager Bill Ackman this year has been United Technologies, the $107 billion Dow component that manufactures industrial equipment.
Bill Ackman, founder and CEO of Pershing Square Capital Management.
Adam Jeffery | CNBC
Bill Ackman, founder and CEO of Pershing Square Capital Management.

Activist investor Bill Ackman's Pershing Square Holdings is off to a strong start in 2019 thanks to some key new stakes and outperformance of prior investments.

The hedge fund reported on Wednesday that its portfolio is up 24.7 percent this year, easily topping the S&P 500's 9.7 percent return. This follows four-straight years of negative returns for his fund. According to the latest holdings, the fund's biggest stakes include Restaurant Brands, Lowe's, Chipotle, United Technologies and Automatic Data Processing.

In a presentation, Ackman noted that Chipotle, ADP and Starbucks were among the biggest boosters to the fund this year. He also discussed a smaller position in Hilton.

Chipotle (CMG)

Chipotle continues to prove a lucrative investment for the longtime stock picker, who remains one of the restaurant's largest stakeholders. The burrito chain buoyed Pershing's gross returns by 6.2 percent in 2018 and is up more than 38 percent this year.

Ackman, whose initial 2016 investment in Chipotle came at an average price of $405, helped bring aboard Brian Niccol as the company's CEO in March. The former Taco Bell executive has long championed innovation and outside-the-box thinking at his restaurants. Niccol has been pushing digital and marketing investments to bring the company back to consistent growth. Digital orders typically mean a higher check for restaurants, not to mention reducing in-store lines.

"Brian and his team have made significant progress turning around Chipotle and reaccelerating growth," Ackman wrote in Pershing Square's shareholder presentation. "Reigniting same-store sales growth is the key priority for 2019."

Ackman and his partners are seeing evidence of burgeoning comp sales. Same-store sales grew 6.1 percent in the fourth quarter, topping consensus expectations of 4.49 percent growth; profits also beat analyst expectations when it reported earnings on Feb. 6.

United Technologies (UTX)

Another strong performer for Ackman this year has been United Technologies, the $107 billion Dow component that manufactures industrial equipment like freight elevators and moving walkways. Though the new stake actually weighed on Pershing's performance in 2018, the stock is up more than 17 percent since Jan. 1.

United Technologies is a "high-quality industrial conglomerate with market-leading businesses in aerospace, elevators and heating, ventilation, and air conditioning," Ackman's presentation read. The "upcoming business separation should be a catalyst for significant share price appreciation."

The activist shareholder added that United Technologies appears well insulted from the current trade dispute between the United States and China and has seen "limited impact" from tariffs. In a 2018 shareholder letter, Ackman said he would explore a breakup of the conglomerate.

Hilton Worldwide Holdings (HLT)

One investment that has yet to post significant outperformance for Pershing Square is Hilton Worldwide. The fund announced in October that it had acquired a 3.7 percent stake in the global hotel operator, shortly after shares hit a more than one-year low on concerns over a slowdown in the hospitality business.

The stock has largely matched the performance of the S&P 500 this year, up 9.6 percent year to date. The S&P 500 is up 9.9 percent since the start of the year. Still, Pershing remains optimistic that its stake will prove itself a smart idea.

"Hilton is a high-quality, asset-light, high-margin business with significant growth potential led by a superb management team," Pershing Square told clients Wednesday. Its "collection of scaled brands and [its] loyalty program create strong network effects for consumers and cost and revenue advantages for hotel owners."