SPECULATION is a dirty word. Market punters are often blamed for
pushing securities prices from extreme to extreme, generating
crises along the way. New regulations have half-heartedly tried
to limit the worst excesses.   But some argue that another
government force is buoying the speculators. To soothe worried
markets, central banks have embarked on an ambitious programme
of unconventional monetary policy. Measures such as quantitative
easing (QE)—printing money to buy things like government bonds
and mortgage securities—are in vogue.   Unconventional monetary
policy has been attacked for prompting further financial gaming.
With piles of cash to play with, the argument goes, investors
have bid up prices of equities, bonds, and commodities. Stocks
and shares have certainly been on the up. From a low in
2009—just after QE began—World Bank commodity price indices have
increased by over 50%. The FTSE 100, an index of stock prices in
Britain, has nearly reached its all-time high.   But a new paper
from the Intern