" Ever since the 2008 global financial crisis, central banks had ventured, not by choice but by necessity, ever deeper into the unfamiliar and tricky terrain of “unconventional monetary policies.” They floored interest rates, heavily intervened in the functioning of markets, and pursued large-scale programs that outcompeted one another in purchasing securities in the marketplace; to top it all off, they aggressively sought to manipulate investor expectations and portfolio decisions. "

― Mohamed El-Erian , The Only Game in Town: Central Banks, Instability, and Avoiding the Next Collapse