Disney and Universal showed in 2017 that if you build something new in Orlando, guests will respond, as the rivals’ biggest additions last year drove the largest gains in attendance.

Walt Disney World’s parks remained dominant in the 2017 Theme Index, an annual attendance report released by the Themed Entertainment Association and AECOM. With the Magic Kingdom still the most-visited park in the world with 20.4 million guests (up only 0.3 percent from 2016), all Disney World parks were ranked in top 10 worldwide and the top five in North America.

The biggest gain came from Disney’s Animal Kingdom. With the addition of the Pandora: The World of Avatar last May, attendance jumped by more than 15 percent to an estimated 12.5 million visitors. This put the youngest Walt Disney World park ahead of Epcot despite that park’s 4.2 percent increase in attendance. Disney’s Hollywood Studios was the only Disney park in the world which saw fewer guests in 2017, with the total number of visitors dropping by 0.5 percent.

Universal’s big 2017 opening was the Volcano Bay water park. Despite only being open for part of the year — beginning May 27 — it attracted an estimated 1.5 million visitors, sixth-most in the world and third-most in North America. At the same time, attendance slipped at other Central Florida water parks like Disney’s Typhoon Lagoon (down 5 percent) and Blizzard Beach (down 7 percent), SeaWorld’s Aquatica (down 10 percent) and Adventure Island in Tampa (down 2.9 percent).

“The 2017 numbers for North America, a mature themed entertainment market, demonstrate a classic wisdom: the need for continual reinvestment as the basis of growth and success, year after year and decade after decade,” the report said.

John Robinett, senior vice president of AECOM’s economics team, said attendance at Orlando parks should only continue to grow with an estimated $10 billion of investment in new attractions, retail, dining, entertainment and hotels slated for the next five years.

It wasn’t all sunshine and rainbows for the area’s theme park giants. Universal’s amazing Harry Potter-fueled growth over the past decade — seeing a 62.5 percent increase in attendance at Universal Studios Florida and Islands of Adventure between 2006 and 2016 — showed signs of leveling off.

Both parks saw only a 2 percent jump in attendance last year; in contrast, Universal Studios Hollywood, in the first full year of its Potter-themed Hogsmeade section being open, saw a 12 percent increase in the number of guests coming through the gates.

For SeaWorld, there was little positive to be gleaned from the 2017 numbers. Its Orlando park saw attendance fall by another 10 percent, knocking it out of the Top 10 list in North American and the Top 25 worldwide. Busch Gardens Tampa, also owned by SeaWorld Entertainment, saw attendance slip by 5 percent.

Its long slump has shown signs of ending with attendance and revenue up during the first quarter of this year. Major new rides and the opening of Sesame Street Place at SeaWorld Florida in 2019 should help attendance in the near future, the report said.

The owner of Legoland Florida, Merlin Entertainments Group, was No. 2 in the world overall with 66 million guests combined across its group of parks, well behind Disney’s total of 150 million but ahead of Universal’s worldwide attendance of 49.5 million. The report didn’t include specific figures for Legoland Florida as it falls outside the Top 25 worldwide and the Top 20 in North America.

Considering Orlando parks’ attendance increased even with parks losing days of operations to Hurricane Irma, the TEA/AECOM report expects Disney and Universal’s turnstiles to stay busy — as long as they make investments in new rides based on “compelling intellectual property.”

“Digital technology has facilitated the ability to leverage IPs more fully in the leisure space,” the report said. “There is a lot of opportunity on the table and we are seeing more IP holders recognize their power and reach for those opportunities.”