Six months after instituting new work rules for union labor at the Convention Center, the facility's managers say there has been a dramatic increase in groups looking to gather in Philadelphia.

Despite the continuing presence of some protesting union members outside the center, bookings are up, with numerous trade and business associations agreeing to return to Philadelphia after noticeable absences, or rebooking after a recent show.

There has been a 20 percent increase in convention-related hotel bookings over last year, according to Julie Coker Graham, executive vice president of the Philadelphia Convention and Visitors Bureau (PHLCVB), the center's marketing arm. The percentage of conventions returning to the city has increased from 17 percent in recent years to 38 percent. And by the end of the year, the PHLCVB expects to have booked 13 major new shows for coming years, with an estimated $535 million in economic impact. This comes after several years of declining interest in Philadelphia by convention planners.

Those trends are indicative of a positive shift in performance and perception at the Convention Center, which had been dogged for years by a reputation as a difficult and costly place, largely because of its Byzantine labor rules.

The center's management said the shift is the direct result of the new rules, which give more latitude to exhibitors in setting up their own booths, and the hiring of SMG, a West Conshohocken company with national experience operating convention centers, to manage the facility last December.

"It has been like night and day," said Gregory J. Fox, chairman of the center's board of directors. "Obviously, we were hoping for change and that things would turn around, but the speed by which they have turned around is terrific."

Ed Grose, executive director of the Greater Philadelphia Hotel Association, said his group has been delighted by what it has seen.

"We are extremely pleased with the changes at the Convention Center," he said. "We are especially excited about the booking base since the changes have taken place. We are on pace not just to be competitive, but to outperform our competing cities."

The recent successes are to be touted Wednesday at the PHLCVB's annual luncheon for the city's hospitality community. PHLCVB also plans to announce its latest coup, the signing of the American Heart Association to bring its 2019 convention and 25,000 delegates to the city.

The association has never held its convention in Philadelphia. The group passed on a previous bid by the city, but decided to reschedule its 2019 meeting for Philadelphia in response to the work-rule changes, according to Graham. The association brings to 18 the number of major conventions - those involving more than 2,000 delegates - booked so far for 2019, the most since 20 in 2013.

The work-rule changes were part of a new "Customer Satisfaction Agreement" (CSA) reached in May with four unions whose members work at the center. The agreement gives exhibitors greater flexibility and work rights to ensure a smoother and less costly experience.

The agreement was reached only after considerable negotiation between the unions and the center. Two unions - the Carpenters and Teamsters - did not sign by the board-imposed deadline and lost their right to work there. They continue to hold periodic protests outside the center, contending they were the targets of a lockout.

"Clearly the center would be better off if it did not have to endure these protests," Fox said. "But our customers have been very understanding. When they see these protests, they see just how hard we have been working to make things better."

Mike Barnes is president of the local stagehands union, which signed the CSA and has taken up much of the work previously done by members of the Carpenters. "In my opinion, we have turned the building from being one of the least desired convention centers," Barnes said, "to one of the most desired convention centers to do a trade show in."

Fox said he is hearing the same from convention planners he has spoken to.

"The hospitality industry is something like a cult. Everybody knows each other," he said. "If something bad happens at a center, somebody in South Dakota knows about it by tomorrow afternoon. The opposite is true, too. Good news spreads like wildfire."

That is evidenced by the National Black MBA Association, which has not held a convention here since 2003.

"We withdrew from hosting our conference in Philadelphia because of labor issues in terms of inflexibility and costs," said Terra Dailey, marketing manager for the Chicago-based association.

The group reconsidered following the new CSA and the reviews the Convention Center is receiving.

"The city has responded and we are pleased with the results," Dailey said. "As a result, we are returning in 2017."

So, in September that year, the organization is bringing 8,000 delegates to Philadelphia - where they are expected to spend $9.6 million.