In the other football, there are some established best practices for NFL teams trying to acquire new players. Teams don't necessarily abide by them, but there's enough data and history to figure out what typically works and what doesn't.
In the college draft, you only want to pick premium-position players early on, i.e. the players at the positions that have the highest average salaries in the league: quarterback, offensive tackle, and pass rusher. And unless you're trying to acquire a quarterback, you don't want to trade away multiple draft picks to acquire a higher draft pick. Instead, you want to trade down to acquire more picks because over the long run, no one is better at drafting players than anyone else. The best drafting teams are the teams that give themselves more chances to draft.
The clear positional delineations, plus established salary and roster rules, make these kinds of distinctions much easier in American football. In soccer, though, everyone plays offense and defense, there are barely any scoring plays, salary info isn't publicly available, there are hundreds of professional leagues, and budgets across and within leagues are drastically different.
But what if we looked at the top 100 transfers in global soccer from the past four years -- the 25 highest fees paid in each season -- to see if there were any trends? What were the worst and best transfers? And what can they tell us about which moves are likely to succeed and doomed to fail?
How to measure a successful transfer
There are all kinds of definitions of success when it comes to a transfer: minutes played, trophies won, goals scored, shirts sold, Instagram followers accrued, etc. But none of those take into account the fact that every club -- including even those run by sovereign wealth funds -- have a limited amount of money they're capable of spending within the vague, ever-changing rules instituted by the sport's various governing bodies.
If you spend $100 million on a player, it means that you didn't spend $100 million on two or three players. There are opportunity costs to every move, and while it's a somewhat cold distillation of how the sport works, there's a simple formula that determines team success: money spent on players, multiplied by the value provided for every dollar (or euro or pound) spent.
The more you spend, the more inefficient you can be. The less you spend, the more efficient you have to be. But even the richest clubs benefit from being efficient with where their money goes. Real Madrid's new era of dominance has been driven largely by a new, efficient approach in the transfer market. Manchester City rarely make truly disastrous transfer moves. And Liverpool's run of success under manager Jurgen Klopp was largely driven by a sensational stretch of player acquisition.
To define efficiency, we're going to compare the fee a team paid for a player with the player's estimated transfer value via Transfermarkt a year after the player was acquired, and the more efficient a move, the better it will rank.