By the time the days lengthen and the weather warms, that perk might help to keep good employees in their posts. Time-limited seasonal benefits are a good answer to this: some firms let their people knock off early on Friday afternoons during the summer, for example. Ben and Jerry’s offers its staff three pints of ice cream and frozen yogurt a day that risks being a benefit which fades into the background, even if its employees are less likely to. Employees can quickly become habituated to something that is unvaryingly available. Perks also work best if they are noticed. Employers who offer help with pet insurance or student-loan debt repayments may be onto something. The rental credit proved much more motivating to drivers. Some drivers were given $100 in cash and others were given a credit equal to the value of a much-disliked rental fee they had to pay to the firm that owned the taxi. In “Mixed Signals”, an enjoyable new book on incentives, Uri Gneezy describes an experiment he conducted with three academics in Singapore, in which taxi drivers there were rewarded if they did a certain amount of exercise. Helping people with things they resent paying for can also be more effective than doling out treats. A discount on a small purchase feels more significant than the same amount off a big-ticket item, for example. Mental accounting is a concept that was coined by Richard Thaler, a behavioural economist, to describe how people put different values on money depending on context. If your perk is a source of controversy, it’s probably not right. Snack cupboards filled with calorific goodies are some people’s version of a sugary paradise, and others’ idea of obesogenic hell. And perks should be motivating to the widest possible group. They should not be touting mindfulness courses if they expect employees to work until they drop from exhaustion.

Firms should not be offering employees access to advice on financial well-being if they pay worse than everyone else. Perks should reinforce a culture, not be undermined by it. But other companies have abandoned the policy because the absence of clear rules leaves employees unsure how much time they can really take off some take less than they did under a fixed allocation of vacation days. Several firms, Goldman Sachs and Netflix among them, tout the fact that they offer members of staff unlimited holidays. Perks that sound great in theory may not work out that well in practice. A poll conducted last year for Trusaic, a software firm, asked American workers what perks they would like to see introduced: the top answer was hangover leave. Asking employees may not always yield good answers. Working out which perks are valuable to workers is hard.

Perks of Office by Liz Rain