The 40-year-old millennial and the 24-year-old Gen Zer are in charge of America right now

• The oldest millennial and oldest Gen Zer are in charge right now - of spending, influence, and the economy.
• The 40-year-old's financial behavior is shaping huge economic markets like housing.
• Meanwhile, the 24-year-old is setting trends, affecting consumer behavior for everyone.
• See more stories on Insider's business page.

The 40-year-old and the 24-year-old are the talk of the town right now.

The oldest millennial, who turns 40 this year, has the most spending power. They've mostly recovered from a decade-long struggle following the 2008 financial crisis, and they're spending on the biggest purchase of their lives: houses.

The oldest Gen Zer, who turns 24 this year, has more sway in consumer behavior. A decade before they replace millennials as the largest spenders, they're already seen as tastemakers, a role every generation takes on during this life stage.

Everything from your buying choices to your lifestyle choices are likely being shaped by the oldest members of these generations.

Meet the people shaping the world you'll live in for the next decade, or two.

The 40-year-old millennial has spending power

Millennials have become the economic driving force in America. They're the largest generation, represent the biggest percentage of the country's workforce, and hold the most purchasing power.

As millennials age and their incomes grow, their spending power is only set to increase. Just look at the wave of coming millennial spending power in the chart below. The 40-year-old leads the way.

While they were some of those hardest hit by the Great Recession, many have made wealth-building strides in recent years. In 2016, their wealth levels were 34% below where they should have been, but as the economy improved and they neared their prime earning years, they narrowed that deficit to 11% in 2019. The pandemic's economic shutdown also enabled the wealthier cohort to sock away even more money.

That means they're the ones doing a whole lot of spending on big ticket items, like housing. Most 40-year-olds have a mortgage, making them the tip of the generational spear that is leading the pandemic housing boom. Not only is this homebuying spree injecting needed money into the economy, it's reshaping the real estate market. Migration out west and to the Sunbelt has been an economic boon for bigger cities in the region, while the "Great American land rush" has seen millennials snap up nearly every starter home on the market.

But there's also something to be said for the 40-year-old millennial who can't spend very much because they haven't financially recovered from the Great Recession. Many are still burdened with debt, like student loans. The affordability crisis they're facing may trigger policy changes such as wiping out student debt, which lawmakers are currently debating.

The 24-year-old Gen Zer has influencing power

As the oldest millennial has entered middle age, the oldest Gen Zer has become a trendsetter.

This is the life stage when a new generation enters the spotlight because they're old enough to begin exerting influence, Jason Dorsey, who runs the Center for Generational Kinetics, a research firm in Austin, Texas, recently told Insider.

That's exactly what Gen Z has done since they've emerged from the pandemic as the new "it" generation. They've sent middle parts, baggy jeans, and Y2K fashion to the streets and skinny jeans and side parts to the wayside, leading the way in consumer trends.

At the center of this cultural shift was TikTok, which blew up during the pandemic. By September 2020, the social media app grew by 75%, expanding into intergenerational use and signaling the growing influence of Gen Z in leading consumer behavior - the same way millennials did with Instagram.

In a little over a decade, Gen Z will be taking over the economy. Gen Z currently earns $7 trillion across its 2.5 billion-person cohort, according to Bank of America Research. By 2025, that income will grow to $17 trillion, and by 2030, it will reach $33 trillion, representing 27% of the world's income and surpassing that of millennials the following year.

With this kind of influence, Dorsey predicts the generation will continue to shift and drive conversation for the next 15 years.

The world is responding. Politicians and lawmakers are debating how to solve the economic issues plaguing millennials, while brands are trying to figure out how they can market to Gen Z. They already know we're living in the world made by the mid-20s and early 40s.