When a twentysomething's budget is tight, her smartphone is far from the first expense to go, suggests a new study from Nielsen.

The survey of 20,000 U.S. mobile customers found that smartphone ownership skews toward the young and the wealthy — exactly as you'd expect.

What is more surprising, however, is this nugget: smartphone penetration among young people in the lowest income bracket is higher than it is among older people in the wealthiest bracket.

Among 18- to 24-year-olds, more than half of respondents who make less than $15,000 each year said they own a smartphone. This might be explained if the parents of many college-age students footing their children's phone bills. Still, even in the next oldest, post-college age group, the percentage of those in the same income bracket who own a smartphone was a mere 13% lower.

Making less than $15,000 in a year doesn't stop 43% of these 25- to 34-year-old mobile customers from paying for a smartphone.

Meanwhile, fewer than 20% of respondents older than 45 who make less than $15,000 said they owned a smartphone.

Older people were less likely to own smartphones than younger people in every income bracket, but it's still telling that so many young people are making room in tight budgets for what many consider to be a luxury expense. It suggests that many young people count smartphones as a necessity.