Americans are on track to hit a big milestone.

This summer, Americans will spend a total of $101.1 billion on vacations this year, representing a 12.5% increase from 2016, according to projections from the Vacation Confidence Index released Wednesday by insurance company Allianz Global Assistance. This is the first time in the index’s eight-year history that spending has exceeded $100 billion.

How much Americans spend on summer vacations depends in part on how old they are. Generation Xers between the ages of 35 and 54 spend the most — an average of $2,628 per person. Comparatively, baby boomers only pay $1,865 on average, and millennials spend the least at $1,373. One theory: Younger travelers may be more willing to rough it than their parents or elder siblings and those with children in school may be forced to book flights and accommodation during the school holidays when it’s more expensive to travel.

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Why are people spending more? Americans’ willingness to spend more on vacations could be the result of their generally positive attitude toward the economy, said Daniel Durazo, director of communications at Allianz Global Assistance USA. “Americans are feeling better about the economy and have loosened their purse strings for summer 2017,” he said. The Conference Board said its consumer confidence index rose to 118.9 in May from 117.6 the previous month. The increase exceeded the 116 forecast of economists polled by MarketWatch.

This confidence could also be a reflection of lower gas prices, according to AAA. The cost to fill up the tank for the Fourth of July holiday weekend was set to be the lowest level recorded in 12 years — and AAA predicts that more Americans traveled for the holiday than ever before.

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And signs that Americans are spending more this year will be welcomed by the travel industry. As MarketWatch previously reported, online searches by prospective travelers to the U.S. have fallen by 6% year-over-year in the first quarter of 2017, according to a study from software company Adobe that analyzed more than 16 billion visits to major travel, airline, hotel, car rental and cruise sites. It has been called a “Trump slump” by travel industry experts because President Trump’s policies have made the country “an uncomfortable place for foreigners,” MarketWatch columnist Rex Nutting wrote in March.

Overall, 44% of Americans said they are confident that they will be able to take a trip this summer, while more than half said they are confident about the possibility of vacationing at some point in 2017 (but not necessarily the summer), the Allianz survey found. However, more than one-fifth of Americans said they aren’t sure they will be able to vacation this year, roughly in line with previous years. The report is based on a nationally representative poll of more than 1,000 adults in the U.S.

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Of course, just because Americans are spending a lot on traveling doesn’t mean they are doing so smartly. Nearly 75% of adults in the U.S. have gone into debt to pay for a vacation, a recent survey conducted by financial planning platform LearnVest found. Driving this trend of debt-fueled vacationing is the fact that many people don’t financially plan for vacations — 55% don’t include the money spent on a trip in their annual budgets. A lack of budgeting is one of the reasons why even the wealthiest families are sliding into the red.