Church Growth = Increased Pastor Salary?

An interesting article at Slate.com, The Almighty Dollar: Are preachers motivated by the desire to save souls or to make cold, hard cash? raises the question of clergy compensation. By researching data from the Oklahoma Annual Conference researchers found:

“It turns out United Methodist congregations gave their leaders a $15 boost (in 2008 dollars) on average for each new member added (about 3 percent of new revenues generated from the membership increase) and cut their pay by about $7 for each member lost.”

The article implies causation, while I believe that the data is clearly correlation. However, it is interesting.

How should clergy be compensated? In what way should pay level be determined for clegy?