Dan Graur suggests that journals should devise a system to tie in the number of papers they publish from senior researchers with the reviewing record of those authors (Nature 505, 483; 2014). This is comparable to linking the amount of milk you drink to the number of cows you milked.

In a market economy, the monetary value of services is determined by the laws of supply and demand. When it comes to the highly skilled service of peer reviewing, the supply is sufficiently high to keep the monetary value at zero.

If, at a constant level of demand, the supply is reduced, then this price would go up. With an increased price, people could become professional reviewers to supplement their salary. Instead of making it harder for scientists to decline their reviewing requests, journals should be allowing market forces to exert their natural effect.