Story from yesterday's USAToday. I found it very interesting although it's a long read:

Couple extracts:

"That's the value of it," Banner says. "It's one thing to say a guy had nine sacks. How many times was he blocked by the tight end, rather than the right tackle?"
On trading up to get Julio Jones
"We knocked off statistic after statistic," Dimitroff says.

He says the offer didn't hinge on the first- and second-round picks dealt. "Everybody understands the first- and second-round picks," he says. "We needed to figure out the value of the other picks."
What did the research reveal? Less than 15% of fourth-round picks become starters.