Now, onto the part where I do some math. This is for the hardnosed, business inclined. There are plenty of assumptions involved here, so it's mostly a ballpark sort of estimate I'm working on. But the orders of magnitude that result should be enlightening, even if the details are off.

Ok. One more warning: for any agents that stumble across this, I'm doing outside business estimation based on broadly available information. Your own business will of course vary in the details, so don't take this as anything other than an estimate, which might be significantly different than how you operate.

Right, that out of the way, let's talk about Alice and Bob. Both of them are star agents. Very good at what they do. Alice works in one end of the pool (let's call it high-midlist) and Bob works in another (let's call it beginners).

Alice averages 40K dollars per advance on each novel she sells. She sells one novel per week, and she makes 15 percent for the life of each contract.

So Alice makes 6K dollars per week from advances on new novels sold. 50 weeks per years, so she grosses 300K dollars per year. She's a one-woman shop, with a full-time secretary and a very good lawyer on speed dial, and she lives in or around Manhattan, close to the action. That's a detailed way of saying she nets out about 120-150K per year, after expenses. Which, let's face it, isn't exactly a lot for living in New York City.

But let's get back to the important part, from a writer's perspective: For every novel writer Zach sends to Alice that gets sold, he's paid her 6K dollars for exactly one week of her time.

What about Bob? Bob works with new writers, he's proud of that, and he's very good at his job. Bob gets 5K dollars per advance for a new writer, and he sells one new writer novel per day. He too gets 15 percent for contract life of each sell, so Bob grosses from advances on new sales on average 188K dollars per year. Bob's frugal, so he lives in New Jersey or out on Long Island, his rent and so on are a little cheaper, so let's say Bob, kind soul and devoted agent searching for new talent, nets about 100K dollars per year just from advances on novel sales.

Note the rabbit in the hat? Let's say Yvonne sells Bob her new novel. In exchange for 750 dollars of the advance, Yvonne has just bought one day of Bob's time.

Let's go further. Let's assume that, Bob and Alice both being very good at their jobs, each and every novel they sell earns out in the first year and continues earning royalties every year after, at 1/2 of each of the previous year's total.

That is, for Alice's case, she expects Zach's novel to gross: year 1 is 40K for the advance, year 2 is 20K for royalties, year 3 is 10K, and so on until the stream of royalties dies off sometime around year 10.

I won't put the exact math in (it's an integral over an exponential function) but this works out to Alice expecting about (15 percent of Zach's gross totals of) 2.5 times 40K dollars lifetime for each of the novels she sells. So, Zach grosses about 97K dollars total over ten+ years of the good selling lifetime of each novel, and Alice gets about 15K dollars in return.

That 2.5 factor is important. What it means for Zach is that he's paid Alice 15 percent, lifetime, of each of his novels that he sends her that sell, for 2.5 weeks of her time. Total. Ever.

Same thing for Bob. The dollar totals are different, but if every one of his new talent first novels breaks out and sells at the same rate (5K advance, 2.5K year 1 royalties, etc) then lifetime, he expects Yvonne's novel to gross about 2.5 times 5K or just over 12K total, lifetime, for each novel sold,
and his cut to be about 1200 dollars lifetime.

And Yvonne, for her first novel, can in turn expect to receive about 2.5 days of Bob's time, total. Ever. For that novel.

(edited to add a few clarifications in Bob and Alice's lifetime cuts)