NEW YORK (MarketWatch) — The interest burden of the federal debt makes for the scariest chart we’ve ever shown.

And we’ve shown some pretty scary ones. Recently we charted the “government grab” — the burden of the federal government relative to Gross Domestic Product. Our conclusion: yes, MarketWatch readers, it really is in some ways in uncharted territory. And it really will take some getting out of. Read “We put the federal budget in perspective.”

And then there was the time we looked at the financial sector as a proportion of GDP. We concluded that author Kevin Phillips was right to say, in his best-seller, “Bad Money: Reckless Finance, Failed Politics, and the Global Crisis of American Capitalism,” that it was strangely distended. Read “Kevin Phillips is still a populist.”

And that levels of public and private debt were unusually high. Read “Debt is not the only problem.”

And look what happened just months after that — the crash of 2008.

In our chart, we look solely at the interest federal debt relative to GDP.

It’s currently roughly where it was 1955-1975. But it’s projected to ramp up astonishingly quickly as the post-crash spending surge kicks in, to levels last seen in 1985-1995. Arguably, those levels were the price paid for ending the Great Inflation of the 1970s. What do we have to show for this more recent binge?

But that’s only the tip of the iceberg. Interest rates now are at historic lows. In contrast, they were at historically high levels the last time the federal interest burden was in this range.

The average interest rate on the federal debt peaked above 9% in 1982. It was still above 6% in 2000.

But it was only 2% in 2010.

Office of Management and Budget, from whom our data is derived, does project an increase in the average interest rate on the federal debt — but only to just below 4% in 2016.

But what if inflation really takes hold? What if the U.S. dollar collapses (in some ways the same thing)?

Simple arithmetic suggests that a return to 1982 interest levels could double the interest burden on the federal debt, to some 6% of GDP.

And that’s without additional borrowing to finance spending to stave off a double-dip recession, bail out politically-connected investment banks, establish new Middle East colonies etc.

The federal government needs low interest rates to help it finance its debt — but low interest rates could trigger inflation, asset bubbles etc.

It’s in a very tight spot.

Reassuring endnote: we’ve been around long enough to remember charting similarly frightening trends in the late 1970s and 1980s. It turned out these trends can be reversed surprisingly quickly by economic growth.

But where is economic growth coming from now?

Edwin S. Rubenstein is president ofESR Researchin Indianapolis.