A new government-seeded investment account for newborns could give ordinary American kids a serious nest egg, which is good news for families who have never owned stocks.

• Every child born in America gets a "Trump account" opened with $1,000 in it automatically.
• Parents, relatives, or an employer can add up to $5,000 a year on top of that.
• At the stock market's long-run return, a girl born this year would have around $170,000 by 18 and over $700,000 by 35.
• Half of Americans own no stocks or bonds at all, so this pulls working families into the market for the first time.
• The pitch is that the kid of a single mom waiting tables ends up with real wealth, not just the kid of rich parents.

Outlook: The math only works if families actually keep contributing and the market delivers its historical returns.