On August 1, 2018, the 10-year Japanese government bond yield, shot through the roof (albeit a very low one). Yields shifted from 0.05 per cent on July 31 to 0.129 on August 1, which was the largest one-day rise since July 29, 2016 (when the yield rose 0.101 per cent). The Financial Times article (August 1, 2018) – Japanese bond market jolted as traders test BoJ resolve – wrote that “traders wasted no time in testing the Bank of Japan’s resolve to loosen its target range for the debt benchmark”. So what was that all about? And what key point does it demonstrate that seems to be lost on mainstream economists who continually claim that government debt is, or can become a problem once bond markets demand higher yields? The Japanese bond market has shown once again that private bond traders cannot set yields on government bonds if the central bank intervenes. Next time you hear some mainstream economist claiming a currency issuing government is running deficits at the will of the investors (read bond markets) politely tell them they are clueless. Japan once again provides the real world Modern Monetary Theory (MMT) laboratory – every day it substantiates the underlying insights contained within MMT and refutes the core mainstream propositions. The bond market over the last month or so demonstrates that the Japanese government is increasingly net spending by using credits created by the Bank of Japan, whatever else the accounting structures might lead one to believe. With inflation low and stable, these dynamics surely put paid to the various myths that a currency-issuing government can run out of money and that central bank credits to facilitate government spending lead to hyperinflation.