Millennials are on the cusp of surpassing baby boomers as the largest generational demographic in the US, yet a startling plurality of them are woefully under prepared to assume the typical trappings of adulthood - like starting a family and buying a home.

And in a detailed report published this week, analysts at ApartmentList illustrated just how wide of a gulf lies between millennials and their economic and financial goals. Perhaps the most surprising finding: Nearly half of millennial renters have zero money saved for a down payment - which doesn't bode well for the housing market, where home prices have surpassed their pre-crisis highs (though signs of weakness are starting to emerge). And just 11% say they have $10,000 saved.

To wit, 72% of millennial renters cite "affordability" as the biggest factor barring them from homeownership. Student debt is another factor: While 23% of college graduates might be able to scrape together enough for a down payment, that figure falls to 12% for those who are currently paying off student loans.

But these aren't the only factors holding millennials back from home ownership. A handful of macroeconomic trends are also to blame: Much of the generation came of age during or in the aftermath of the Great Recession, resulting in limited opportunities and stagnant wage growth in the crucial early stages of millennials’ careers. Construction of new single-family homes has lagged significantly in recent years, leading to a severe shortage of starter homes.

Roughly 9 in 10 millennial renters want to purchase a home; but just 4.4% plan to do so within the next year:

The "burden of affordability" primarily manifests in millennials inability to scrape together enough money for a down payment:

And even if they can manage to save some money, the amount needed for a down payment is often larger than they think:

And at the present average savings rate, most millennials will need more than two decades to save up enough for a down payment.

Ironically, millennials with the highest incomes receive the most help from family for their down payments.

And as we mentioned above, student-loan debt is one of the biggest obstacles absorbing all of the money that would otherwise be saved for a down payment.

The upshot of this is that, instead of accumulating wealth in a home - which has always been the primary source of value for American families - millennials will continue throwing it away on rent, which offers them no return and no security later in life.