But they can only approximate when the cycle will turn, and sometimes, as with everyday weather predictions, they are wrong.
It was inevitable that as the cycle of fashion turned, they would lose favour in the early 1990s.
"People who are great deal makers may do well in the growth part of the cycle but flounder when the cycle turns," he said.
The cycle turned and the goddess lost her power.
By periodically bringing man back to the mythical age, these liturgical cycles turn time itself into a circle.
Then, with costs still rising, losses would inevitably follow, until the insurers again raised their rates and the cycle turned.
But, for the moment, the cycle has turned.
By the fifteenth century, cycles had turned again.
It has reached the tipping point where the cycle of restored growth could turn Africa into an equal player on the global stage.
"They are fundamental, and will not go away as the cycle turns."