Look no further than the widening generational wealth gap to see just how financially behind millennials are.

Millennials earn 20% less than baby boomers did at their age, according to a new report by think tank New America. These findings come after a MagnifyMoney study of Federal Reserve data on household assets and liabilities from earlier this year.

The study found that the average American millennial household today (ages 20 to 35 in 2016) has an average net worth of $100,800, while the average American baby boomer household today (ages 52 to 70 in 2016) has a net worth of $1.2 million (all values are adjusted for inflation), reported Mallika Mitra for CNBC. That means that baby boomer households in 2016 had twelve times the net worth of millennial households.

A gap in wealth between these age groups makes sense because baby boomers have had more time than millennials to accumulate wealth — but comparing that wealth gap to those of previous generations shines a new light on the findings.

In 1998, the average household aged 20 to 35 had a net worth of $103,400, while households aged 52 to 70 had a net worth of $747,600, MagnifyMoney found — roughly seven times more than the younger households.

That means the wealth gap between older households and younger households has nearly doubled in the past 20 years, climbing from seven to twelve times the net worth.

In that time frame, the average net worth for households ages 20 to 35 has declined by $2,600, while households ages 52 to 70 have seen a $452,400 increase in net worth.

Read more: Millennials have been called the 'brokest' and the 'richest' generation, and experts say both of those are true

The Great American Affordability Crisis is to blame

As a refresher, net worth is one's entire personal assets minus all their liabilities. MagnifyMoney's analysis reveals that millennials have more liabilities — debt — than any other age group studied.

Much of that debt takes shape in student loans, thanks to college tuition that has more than doubled since the 1980s — the national student-loan debt total is more than $1.5 trillion, and the average student-loan debt per graduating student in 2018 who took out loans is $29,800.

According to a report earlier this year by Merrill Lynch Wealth Management, 81% of early-adult households ages 18 to 34 carry a collective debt of $2 trillion, including student-loan debt and credit card debt.

Meanwhile, as Mitra reported, rising housing costs also play a role. First-time homebuyers today will pay 39% more than first-time homebuyers did nearly 40 years ago, according to Student Loan Hero. That means millennials are less likely to buy a home, making houses an asset more boomers than millennials have.

There's also the aftermath of the Great Recession, which created a financial domino effect for millennials that put them on a slow path to wealth accumulation. It hit millennials born in the 1980s especially hard: Their wealth levels are 34% below where they would most likely have been if the financial crisis hadn't occurred, according to a report by the St. Louis Fed.

The recession also made millennials wary about investing, Mandi Woodruff, executive editor at MagnifyMoney told Mitra.

Ultimately, the generational wealth gap increase is an effect of The Great American Affordability Crisis, in which rising living costs, increasing student-loan debt, and the ongoing fallout of the recession are creating serious financial struggles for millennials.