In the battle for the hearts and wallets of today's teenagers, it's YouTube over Netflix, Crocs over Birkenstocks and iPhones over just about everything else.

That's among the findings of Piper Jaffray's most recent peek into the lives of America's up-and-coming consumers. The Minneapolis-based investment banker has been doing a survey of young people's shopping habits every six months since 2001, providing a window into what's ahead for businesses and the consumer economy.

But the survey wasn't all about food (where boys spend their money) or apparel (where girls' money goes) or about Amazon (the top online shopping site).

The report found the lowest spending among teens in eight years — an important finding, according to Piper Jaffray's senior research analyst Erinn Murphy.

About a third of the teens said they felt the economy was getting worse, compared to about a quarter who felt that way a year ago.

Self-reported spending among teens dropped 4% from a year ago and 10% since the last survey in the spring. At $2,400 in annual spending, it was the lowest level since fall 2011.

About 9,500 high school students in 42 states were surveyed for Piper Jaffray's most recent "Taking Stock of Teens" report. The average age was 15.8 years.

The so-called Generation Z is considered an influential consumer group that contributes about $830 billion to the U.S. retail economy each year, according to Fung Global Retail and Technology.

Among this digitally native demographic, 83% of teens have an iPhone, and they give it high brand love. The survey found that 86% expect their next phone to be an iPhone.

The report noted that girls have "reprioritized" their spending on eating out and footwear, while backing off purchases of handbags and cosmetics.

And while Crocs are enjoying a slight comeback (No. 7 on the list of favorites), Nike reigns supreme as fashion becomes ever more casual overall.