David Phillips and his colleagues at the University of Southampton, in England, show that childhood infections reduce the probability of acquiring insulin-dependent diabetes.

ECONOMIST: Plagued by cures

Spending more time in school did reduce the probability of a teenage pregnancy, but on a much smaller scale than the effect of a pregnant sister.

BBC: Teenage pregnancy is 'contagious'

Measures that increase the resilience of financial institutions, such as the new Basel III capital and liquidity standards, will reduce the probability and frequency of a sudden liquidity shock.

FORBES: Bank Of Canada's Carney Warns About Loss Of Global Liquidity

Now the debate is over the extent of the vulnerability, the probability that it will occur, how to reduce the vulnerability, and how to respond to an attack.

CENTERFORSECURITYPOLICY: Center For Security Policy

"At the margin, this could reduce demand, but nobody should have been buying this stuff on the basis there wasn't a material probability of at least one junk rating at some point in the future, " Mr. McNamara said of the bond sale's postponement.

WSJ: Slovenia Bond Sale Postponed