Spending on business travel around the world puttered along in 2016, rising a less-than-expected 3.5 percent to $1.26 trillion, according to a new report this week.

The outlook, according to the Global Business Travel Association, improves somewhat this year and more moving into 2018 and beyond — but as recent history has shown, those forecasts could be dashed by unexpected global events.

“Stronger footing in emerging markets and continued economic stimulus in the developed world has supported global stability leading to a positive forecast that is unfortunately clouded with more uncertainty than we have seen in decades,” GBTA executive director and chief operating officer Michael McCormick said in a statement.

After increasing nearly 4 percent in 2015, spending was expected to grow 5.2 percent last year but fell short. The new outlook calls for 5.2 percent growth this year, accelerating to 6.1 percent in 2018 and about 7 percent the following two years. Those expectations are “pending many global uncertainties,” however, including the threat of terror, geopolitical tensions, immigration crackdowns, and trade policy changes.

“The renewed optimism for business travel activity is being driven by an uptick in global trade, expected improvements in the manufacturing sector, economic improvements in emerging markets and shifting currency dynamics,” the report says. “Many downside risks remain, however. Most notably, public policy in the U.S and abroad has the potential to drastically change the global business travel environment.”

The outlook points out that some unknowns in the U.S. could turn out to be good for business travel: President Donald Trump’s intentions to lower corporate taxes, reduce regulations, and invest in infrastructure could all spur more business travel.

But restrictions on trade policy, travel bans, and restrictions on electronics — which just gave way to stepped up security measures — could be harmful, GBTA said.

“Policies that would have an incredibly negative impact on business travel activity include any policies aimed at reducing the free movement of goods, services or people,” the report said.

In the UK, the worst fears about the decision to leave the European Union have not been realized as the economy has continued to grow even while the value of the pound has dropped.

But the Brexit impact won’t be clearly understood until negations between the UK and European Union member states are completed.

“Less restrictive trade policies that mirror exiting agreements, so-called ‘soft Brexit,’ would help to ensure that business travel activity remains on a healthy trajectory. This is thought to be the most likely scenario,” the report says. “Should the UK go the ‘hard Brexit’ route, with more restrictive trade policies, business travel activity would likely suffer.”

Still, the outlook expects the UK to join India and Indonesia in averaging double-digit business travel spending growth over the next five years. Other European countries including Norway, Sweden, Spain, France and Germany are also expected to see strong growth.

In a separate report, released this week with Carlson Wagonlit Travel, GBTA’s education and research arm said travel prices are expected to rise next year.

The 2018 Global Travel Forecast indicates that airfares worldwide are expected to be up 3.5 percent, while hotel room prices will increase 3.7 percent. Ground transportation costs should be more stable; they are forecast to rise 0.6 percent.

“The higher pricing is a reflection of the stronger economy and growing demand,” Kurt Ekert, president and CEO of Carlson Wagonlit Travel, said in a statement. “The global numbers from this forecast should be considered strong leading indicators of what 2018 will mean for global businesses, as we anticipate higher spending.”

Photo Credit: Spending on business travel across the globe is expected to increase 5.2 percent this year. The Grand Hyatt in Shanghai is pictured here. staalnakke / Flickr