Go, go, go

The U.S. economy is a galloping horse, a jet plane that's reached altitude, an express train hurtling forward in the days before the subways started creeping: Pick your metaphor, and it's mostly true.

In the second quarter of the year, growth hit an estimated 4.1%, a significant acceleration over the previous four quarters, when it had bounced around between 2% and 3%.

Four percent is hardly unheard of; the economy reached the same or higher rate of growth four times in Barack Obama's eight years, four times under George W. Bush, and 12 times under Bill Clinton.

Still, it's robust, and many underlying economic indicators look healthy. President Trump can rightly boast. We hope it continues and will give him and Congress credit when and where it's due. But beware real potholes ahead. A skewed tax cut that gave the largest benefits, even on a relative basis, to the richest people and corporations, is blowing a hole in the federal balance sheet. At this rate, the nonpartisan Congressional Budget Office predicts the national debt will be nearly 100% of the gross domestic product by the end of the next decade.

Which is to say, major tax hikes or benefit cuts loom on the horizon.

As do the on-the-ground effects of a trade war Trump only recently launched, which is hammering industries across the country — and forcing Washington to hand out billions in federal rescue money. Fears of coming tariffs, in fact, goosed export numbers in the last quarter.

Average wages of private-sector workers registered almost no growth over the last year.

Applaud an economy that's going great guns, but keep a careful eye on stubborn or growing problems beneath the surface.