At the time many military leaders recognized that poor nutrition was a significant factor reducing the pool of qualified candidates for service.

WHITEHOUSE: Bringing Healthy, Affordable Food to Underserved Communities | The White House

These recent gains in receipts confirm that a strong economy is the most important factor in reducing the deficit.

WHITEHOUSE: Testimony of Director Bolten

Obama will probably point out Tuesday night that economic growth is the essential X Factor to reducing long-term deficits and debt.

CNN: Obama's chance to lead -- or kick the can down the road

Iraq's Awakening Councils, drawn from among the country's Sunni Muslims, have been seen as a key factor in reducing violence across the country since 2006.

BBC: Suicide car bombing in central Iraq kills six

While acknowledging policing isn't the only factor in reducing gun violence, they cite the all-time low number of slayings in a city where most people are killed with guns.

WSJ: Experts back NYC's link of gun laws, lower crime

Vitamin D also appears to play a role in healthy immune function and reducing inflammation, a risk factor for numerous diseases including cancer, heart disease and diabetes.

CNN: How much vitamin D should someone over 55 take?

As well as serious crimes like burglary, it has also proven effective in reducing antisocial behaviour on our streets, a key factor in whether people feel safe and comfortable in their communities.

BBC: High-def CCTV cameras risk backlash, warns UK watchdog

It is absolutely obvious to us that the key factor here is the fact that over the years airlines have been continually reducing the space between seat rows to cram more and more people in.

BBC: News Online

The current-account deficit, now around 5% of GDP, is a key factor: if capital flows into America slowed even more sharply, or dried up, the adjustment involved in reducing the current-account deficit could be painful both for America and the rest of the world.

ECONOMIST: Time for a rethink | The