Thanks for the link... It's still a little over my head, but I'm beginning to understand. In poking around for a more simple explanation, I found this 2014 piece in Forbes.
https://www.forbes.com/sites/jeffreydorfman/2014/07/12/forget-debt-as-a-percent-of-gdp-its-really-much-worse/#2d54e91f53ba
It will be interesting to see if the coming budget plans will move the needle.
I'm rarely a fan of "contrarian" experts. The author is not only "contrarian" on this issue relative to the general field (economists in general) but also dismisses even a "common sense" analysis of his approach on the subject.
Ignoring the massive short-comings in trying to equate national economics and finance with a household budget, there's a few other things he completely ignores.
Lets talk about his "major" point that a family's debt becomes problematic at more than 3x their annual income. Let's ignore the fact that the average mortgage balance is over 3x the average household income and yet most people manage to have no problem paying their mortgage and, instead, let's look at "why" that 3x number is being used.
Owing more than 3x your annual income is considered "problematic" because it results in the household having to spend a significant percentage of their annual income "servicing" that debt. In fact, for a "normal" family (we'll stick with the simplistic, if inaccurate, comparison the anti-debt people prefer to use for now), having that kind of debt would mean they're spending close to (or more than) 1/3rd of their gross income just servicing their debt. I think we can all agree with the author that spending over 1/3rd of income on debt is hard. So that family of 3 making $50k/year borrowed $314k to buy a house that costs them 36% of their gross pay each month ($1.500), and now they're feeling the burn of those payments impacting their ability to spend and/or save money elsewhere.
What if, however, that mortgage was at 0.75% interest with a 50 year loan term? How would that impact their finances? Well, now they're looking at a $300/month payment using up about 7% of their gross pay. Assuming they were going to live for 200 years, no one would tell a couple that paying 7% of their income for their residence was a financial problem because that's a very reasonable amount of their salary to be paying servicing their debt.
So, what are we paying to service our debt as a country? Well, in that guy's 2010 time-frame we spent ~19% servicing debt if we only use tax revenue to keep the "family" analogy going. By last year that had dropped to 13%. So, our debt last year was costing us about the same as if a family making the average income bought a $115k home at 4% interest on a 30 year loan. Does anyone here think there's a financial problem if a household making $50k/year has a $115k mortgage at 4% as their only debt??
There are plenty of things to worry about in the markets if one wants to speculate about potential problems, making payments on the national debt isn't one of them right now imo.