Big spenders? Retail sales report mirrors Millennial buying habits.

Fingers tapping away at her smart phone, Jessica Nguyen Phuong walks into an Apple store to buy a MacBook charger. She has an iPad and an iPod. In a few months, she may replace her smart phone, again.

But a car? She doesn't even have a driver's license. The senior at Scripps College in Claremont, Calif., expects to go into marketing and change cities often, so she's not planning on getting a license soon. She may never buy a car.

Companies are keeping a wary eye on consumers like Ms. Nguyen Phuong, one of 80 million Millennials in the United States. Born between 1980 and 2000, they're America's largest generation and the country's newest cohort of consumers. But it's not clear that they're going to replicate their parents' mall-shopping ways. Millennials have made catalog shopping irrelevant and e-commerce boom. They've been slow to buy cars and homes – and, correspondingly, all of the major appliances and retail goods to set up a household.

The latest retail sales figures from the US Commerce Department seem to bear that out. Retail sales in the US slipped 0.1 percent overall in September, but they climbed 0.4 percent when auto sales weren't factored in (auto sales fell 2.2 percent last month). The biggest gains were in smaller, discretionary categories. Electronics sales rose 0.7 percent, and food and beverage sales saw the biggest monthly gain at 0.9 percent. 

Companies' big concern: If Millennials buy fewer big-ticket items does that mean they'll spend less in their lifetimes than their boomer parents?

With economic recovery and job-creation proceeding at a snail's pace, it's too soon to tell. Millennials may simply be delaying big purchases until they make more money. One thing is clear: Millennials and their boomer parents are different kinds of consumers.

Millennials are "cosmopolitan in nature, very impulsive, live in the 'here and now,' and value digital technology more than older generations," says Johan Mohd Sani, content director at Hanover Research, an information-services firm based in Washington. "I don't think companies are doing enough to attract them right now."

Sometimes, however, no amount of marketing can alter life choices. Take housing. After reaching a historic peak of 69 percent in 2004, the percentage of Americans owning a home has declined steadily to a more normal rate of 65 percent. Some analysts think it could slip below historical norms. Building materials, meanwhile, creeped up 0.1 percent last month, according to the Commerce Department. 

"We've gone from a homeownership society to a renters' market," says Anthony Sanders, a professor of real estate finance at George Mason University in Fairfax, Va. Unemployment, rapidly changing careers, and delayed marriages make it less likely that young people will buy a home. Another factor: a burgeoning $1 trillion student loan debt. While almost 10 percent of 25-to-30-year-olds with student debt qualified for a mortgage in 2005, just 4 percent qualified last year, according to the Federal Reserve Bank of New York.

"A home isn't on the radar," says Mazin Melegy, a 20-something professional at the Woodrow Wilson National Fellowship Foundation in Princeton, N.J. "With the nature of my career goals, I can't imagine a time when I will be staying put for longer than a few years."

Even Bryan Hayes, a 33-year-old working in the education industry who just bought a home in central New Jersey, says that for most Millennials, "coming up with the down payment is extremely difficult and often prohibitive."

The same uncertain, city-to-city lifestyle that keeps many Millennials from buying a home may sour this generation on another big purchase: cars.

Mr. Melegy, who has been driving a used car since 2006, says he is delaying buying a new car "for as long as possible.... I'm unsure of how long I am going to remain in the country, and so the purchase might not make much sense. Of course, finances are always tight."

It's a sentiment reflected in the numbers. Americans ages 16 to 34 drove, on average, 23 percent fewer miles in 2009 than they did in 2001, making them the age group with the largest decline in driving over those years. "The Driving Boom is over," Phineas Baxandall, senior analyst at the U.S. PIRG Education Fund, a Boston-based education and research nonprofit, said in a May report.

High gas prices may have something to do with the decline. Also, Millennials are drawn to more urban, walkable neighborhoods, unlike their suburban parents, and are more willing to use public transportation, bike sharing, and car sharing to get around.

Not all experts say Millennials are swearing off cars. This could be the "generation that leads us away from traditional gasoline-powered vehicles," says Craig Giffi, vice chairman and automotive leader of New York-based consulting firm Deloitte, in a 2012 report. Other experts believe that once the economy picks up, Millennials will probably return to auto dealerships, buying hybrid and gas-powered cars alike.

"We're looking at people who have come into employment age at the worst possible time in maybe 80 years," says Lacey Plache, chief economist at automobile website Edmunds.com. "That really has an impact on Millennials' ability to buy large durable goods." But as long as jobs increase and young adults begin forming households, "this generation will be there for the auto industry."

If Millennials are delaying big purchases, it doesn't mean they're not spending. They currently spend $600 billion a year on retail. By 2020, that number will swell to $1.4 trillion, or 30 percent of all retail sales, according to consulting firm Accenture. And they're buying electronics – lots of them.

"Millennials are not just using electronics. Actually, they're starting to really require [them]," says Alison Paul, a vice chairman at Deloitte.