U.S. business travel spending will increase by 3.1% in 2015 and 3.7% in 2016, yet the global oil price collapse and economic weakness in China, Russia and the Middle East will dampen the outlook for growth this year and next.

These findings are part of the “GBTA BTI Outlook – United States 2015 Q3,” a report by the Global Business Travel Association (GBTA) Foundation and sponsored by Visa Inc.

“Growth in U.S. business travel spending is softening as result of the uncertain macro-economic environment,” said Michael W. McCormick, GBTA’s executive director and COO. “While the number of trips are up, total spending per trip is down. That can be linked to growing uncertainty and risk associated with the global economy, especially in China, Russia and the Middle East, and the global collapse in oil prices. This should sound a clear note of caution for the overall U.S. economy.”

The Q3 report represents a downward revision from the one released in July — when growth was projected to grow at 4.9% in 2015 and 5.4% in 2016. The revision can be attributed to three key factors, according to GBTA:

1) U.S. companies are becoming more selective in authorizing business travel abroad as a result of global economic uncertainty and risk: While we expect 5.4% growth in International outbound business travel volume this year, spending growth rates will be slashed by more than 50% from 2014 (from 8.6% to 3.4%).

2) Inflation in the business travel sector will be nearly flat (0.5%) in 2015 and modest (3%) in 2016, primarily due to the collapse of global oil prices: While the volume of U.S. originated trips will increase 0.7% from 495.8 million in 2014 to 499.2 million in 2015 and 514.8 million in 2016, the total growth rate for spend is actually down. This is especially true in two areas — air travel spending will decrease by 3.4% in 2015 and ground transportation spending will decrease by 7.7%.

3) Actual (as opposed to projected) business travel figures, which were revised to indicate higher trip numbers and lower spending figures for 2014.

Additionally, the study found the collapse in global oil prices is finally beginning to impact consumers, particularly when it comes to air travel spending, according to the GBTA report. In 2015, the average airfare for a domestic roundtrip is $379, compared to $392 in 2014.