Travel is becoming less a discretionary activity and more of a necessity, especially if you subscribe to Abraham Maslow's theory that puts human needs in a hierarchical pyramid.

As such, once the basics of food, shelter and safety are in hand, the more complex needs of sharing, belonging, self-esteem and self-actualization take hold. Travel presents a fast-track to these higher requirements.

Passing into a new year, many of us take stock of our lives and accomplishments within this structure and make plans for how to climb up the ladder to self-actualization and purpose. Much of that thinking will be represented in the field of travel in 2018 as the industry responds to ever more complex demands from a comfortable but restless traveling public.

Strong economy means strong travel spend

Despite a dip in overall dollar numbers for the travel industry in 2016, and chaotic, unpredictable world events in 2017, the big picture for travel remains strong. The economy is strong, the stock market reaches new highs regularly, corporations are optimistic, and unemployment is relatively low.

Overall, U.S. travel abroad ticked up more than 16 percent in 2017, according to the U.S. International Trade Administration. By all accounts — barring catastrophic disruptions — such momentum is expected to continue.

A recent AARP Travel survey predicts:

• Baby boomers — those born between 1946 and 1955 who comprise around 15 percent of the U.S. population — expect to take four or five leisure trips next year, spending an average of almost $6,400 on leisure travel in 2018 (most say this will be the same or more than they spent in 2017).
• Millennials estimate they will shell out about $6,800 for vacations and Gen Xers $5,400.
• More employed boomers will use all or most of their vacation time in 2018, more than in 2017 (68 percent compared to 59 percent).
• 74 percent of millennials expect to bring work along on a trip; 65 percent of Gen Xers plan to do the same; but just 56 percent of boomers are likely to work while out of the office. Of those boomers who do expect to work on vacation, most try to limit it to just 10 percent of their leisure time.

Travel must be transformative

More than ever, travelers want to return home truly enlightened and transformed — having given up plenty of time glued to personal tech and social media to assimilate their destination "firsthand."

Travelers will prefer to go off the beaten path and immerse themselves in an "exclusive" excursion that is at once unusual and relatable. Or they'll shove off on a special, personal mission — such as exploring one's roots.

Either way, for that immersive stay or experience in a new or emerging destination, they'll want an angle on the trip that is, if not transformative, then hugely memorable. This is especially true for luxury travelers interested in experiencing new and emerging places.

"We tend to talk about luxury travel, adventure, family ... all these different travel niches. When it comes down to it though, it's the transformative nature of travel that is the single biggest motivator," Matthew D. Upchurch, chairman and CEO of Virtuoso, a network of luxury travel advisers, told U.S. News & World Report.

"It's in those moments of discovery that you make genuine human connections; that you're transformed because of your travels. And in that sense, as well as many others, travel is a force for good."

Nontraditional, immersive spaces are in demand

Airbnb.com not only tracks and ranks destination cities, hosted "experiences" and home rental stays, but it also tracks trending "types" of spaces that are popular on its short-term rental booking engine.

Airbnb's 2018 Travel Trends survey showed that more rustic and nontraditional homes have enjoyed the greatest increases in bookings. Especially prominent were travelers' interest in nature locations. Nature lodge bookings were up more than 700 percent; ryokans (traditional Japanese inns) were up 600 percent; yurts 155 percent; and RVs 133 percent.

It is likely demand for these nonmainstream accommodations will continue to pick up steam, especially as more such inventory comes online.

Experiences will grow; dining experiences most popular

Airbnb's Experience program, which allows guests to reserve local activities led by locals and hosts, also has shown staying power. The most popular experiences will continue to be dining-related, but music-related experiences are expected to gain in 2018.

In 2017, food and drink accounted for 29 percent of total experience bookings. Total weekly experience guests have increased 20-fold year-to-year. For 2018, outdoor excursions and live concerts will lead the market, and millennials are again quite leading the charge: Two-thirds of experience bookers are aged 35 and younger.

Airbnb’s five most popular experiences include Lisbon's Best Flavors (Lisbon); Hollywood Sign, Walk to the Top (Los Angeles); Secret Concert in a Treehouse (London); Raise a Glass to Prohibition (New York); and Brixton Hidden Jazz Club (London).

Online bookings by smartphone will only increase

Software vendor Trekksoft has some key takeaways about booking travel via smartphones: About two-thirds of travelers now plan and execute their travel and reservations on mobile devices. The research and planning can start between one and three months prior to departure. It can continue well after they’ve reached their destination.

After researching on a smartphone, 79 percent of smartphone travelers complete a booking. The convenience factor means gross bookings for online tours and attractions, to use just one example, will more than double from $9 billion in 2015 to $21 billion in 2020 — with the vast majority booked by smartphone, says industry analyst Phocuswright.

Online direct bookings will drive tour and activity profits

Even mom-and-pop tour operators need to acknowledge that consumer behavior has dramatically shifted to online, according to Trekksoft. Hence, these bookings have become increasingly last-minute and in-destination decisions.

One thing is for sure: More and more small operators will accommodate direct bookings, and more last-minute and in-destination bookings. Hardware and software will rise to meet that reality and will then expand in scope.

If direct bookings aren't in the cards for certain tour operators, they must invest in tech and work with online resellers as much as possible to accommodate bookings via smartphones and other mobile devices.