Even the explainers in finance are shitty. An inverted yield curve means you make more money loaning it to the government for two years than you do loaning it to the government for ten years. Because bonds are sold auction-style the price is what someone can sell it for. When everybody in the business of loaning money to the government is most comfortable loaning it for two years rather than ten years, it stands in as a powerful signal that people with money don't want to loan it out for very long. Generally because they think there are better things they can do with it. Like wait for prices to come down. And buy later.
What I got from the article was that the graph of expected average yield on bonds plotted over time used to be a graph going up, but is now flat or downward due to long term expected yields plummeting. Right? Not that I disagree - it is kinda confusing to say a decrease of future yields represents a 'flattening'. Maybe it's because I'm about 2/3rds into Piketty, but this explanation seems par for the course for economists.
I think that misses the subtly of how bond yields work, which is sort of inverted from normal products. Bond yields dropping means that demand is increasing, and the government therefore gets to promise a lower future return to attract buyers. Increasing bond yields, by contrast, indicate the demand is low, either because faith in the government is shaken, or people see more profit on other investments. So long term prices dropping while short term process are increasing essentially says people are boarding up the windows for an expected storm. Although, as is pointed out on the article, the governments of the world have never had balance sheets like the ones they have now, so who knows if past performance is an indicator of future results.
If they were honest, they'd adopt betting pool terminology rather than rootin' tootin' highfalootin' econ terminology. Then they'd call it a point spread. Then it wouldn't be an "inverted yield curve" it would be a "negative point spread." Because that's what's being discussed here - the idea that long-term bets pay worse than short-term bets which is an inversion of the natural order.