Now shale and other unconventional as well as new conventional gas finds have increased that period to 200 years or more, by some estimates.

ECONOMIST: An unconventional bonanza

Estimated to be around the size of Texas, this contaminated area of ocean has by some estimates more plastic than food for marine life.

CNN: Boat of plastic to set sail with environmental message

By some estimates, generics account for more than 90% of the market for AIDS medications.

FORBES: AIDS Drugs �C For Profit Or Not?

By some estimates, methane hydrates contain more energy content than all other known fossil fuels combined.

FORBES

By some estimates, it will take more than eight years of normal sales to clear the stock of houses now held by banks.

ECONOMIST: The housing market: Double-dip drama | The

His prescription: more troops -- upwards of 40, 000 by some estimates -- with the goal focusing on securing Afghan towns and cities in certain areas.

CNN: Afghanistan haunted by ghost of Vietnam

Two initial British attempts failed to rescue Lucknow, only emboldening more Indian soldiers and landowners to revolt until 30, 000 rebels, by some estimates, bombarded the Residency with artillery fire.

NPR: Lucknow Is For Lovers

Meanwhile, shortages created a crime-ridden black economy that, by some estimates, was worth as much as 30% of the real one, perhaps more.

ECONOMIST: Welcome to the new world disorder