WHAT: A declining market for high-risk mortgage bonds was falsely kept alive as banks bought their own products to boost buyer demand, according to ProPublica, an investigative journalism think-tank headed by former Wall Street Journal editors.

WHO: Primarily active in the price-boosting scheme was Merrill Lynch, but also Citigroup, UBS and others. ProPublica reports that it became a common industry practice by late 2006.

WHY IT’S OUTRAGEOUS: Those ultimately near-worthless mortgage-backed securities were at the heart of the 2008 housing meltdown that still mires the global economy in stubborn recession.