Bill Moyers is shrill:
One of the biggest changes in my lifetime is that the delusional is no longer marginal. How do we fathom and explain the mindset of violent exhibitionists and extremists who blow to smithereens hundreds of children and teachers of Middle School Number One in Beslan, Russia? Or the radical utopianism of martyrs who crash hijacked planes into the World Trade Center? How do we explain the possibility that a close election in November could turn on several million good and decent citizens who believe in the Rapture Index? That’s what I said—the Rapture Index; Google it and you will understand why the best-selling books in America today are the 12 volumes of the 'Left Behind' series that have earned multi-millions of dollars for their co-authors, who, earlier this year, completed a triumphant tour of the Bible Belt whose buckle holds in place George W. Bush’s armor of the Lord. These true believers subscribe to a fantastical theology concocted in the l9th century by a couple of immigrant preachers who took disparate passages from the Bible and wove them into a narrative millions of people believe to be literally true.

According to this narrative, Jesus will return to earth only when certain conditions are met: when Israel has been established as a state; when Israel then occupies the rest of its 'biblical lands;' when the third temple has been rebuilt on the site now occupied by the Dome of the Rock and Al Aqsa mosques; and, then, when legions of the Antichrist attack Israel. This will trigger a final showdown in the valley of Armageddon during which all the Jews who have not converted will be burned. Then the Messiah returns to earth. The Rapture occurs once the big battle begins. True believers 'will be lifted out of their clothes and transported to heaven where, seated next to the right hand of God, they will watch their political and religious opponents suffer plagues of boils, sores, locusts and frogs during the several years of tribulation which follow.

From the horse's mouth:
The Rapture Index has two functions: one is to factor together a number of related end time components into a cohesive indicator, and the other is to standardize those components to eliminate the wide variance that currently exists with prophecy reporting.

The Rapture Index is by no means meant to predict the rapture, however, the index is designed to measure the type of activity that could act as a precursor to the rapture.

You could say the Rapture index is a Dow Jones Industrial Average of end time activity, but I think it would be better if you viewed it as prophetic speedometer. The higher the number, the faster we're moving towards the occurrence of pre-tribulation rapture.

Rapture Index of 85 and Below: Slow prophetic activity
Rapture Index of 85 to 110: Moderate prophetic activity
Rapture Index of 110 to 145: Heavy prophetic activity
Rapture Index above 145: Fasten your seat belts

As of September 27, 2004, the Rapture Index stands at 154.