sixfeet and wondering--I'm sorry, I should have explained it better. The 1 for 3 comes from a descent rate that gives you a 1000' descent every 3 miles. It was the benchmark we used when I was at my previous company.
Now, the Gulfstreams (and I assume the other biz jets) will do much better than 1 for 3 at idle power unless you have a good tailwind. That's just where I start and I adjust as necessary.TC