The idea of being paid for the time spent assessing colleagues' research might only fleetingly cross most academics' minds.
The advancement of the academy's collective body of knowledge has traditionally been held to be reward enough for the time and effort put into peer review.
But a new report has attempted to quantify in cash terms exactly what peer reviewers are missing out on. It puts the worldwide unpaid cost of peer review at £1.9 billion a year, and estimates that the UK is among the most altruistic of nations, racking up the equivalent in unpaid time of £165 million a year.
"This is a huge hidden subsidy to the system which no one has ever quantified," said Michael Jubb, director of the Research Information Network, which commissioned the study Activities, costs and funding flows in the scholarly communications system in the UK, undertaken by Cambridge Economic Policy Associates.
The assessment of peer-review costs is part of an attempt to provide - for the first time - a picture of the costs of the entire scholarly communications system, from the production of research outputs to the reading of them, focusing on their publication, distribution and access.
The study estimates that the global cost of undertaking and communicating the results of research reported in journal articles is £175 billion a year, made up of £116 billion for the costs of the research itself and £25 billion for publication, distribution and access to the articles (which includes the hidden costs of peer review) and £34 billion for reading them.
It also estimates that the UK is a "net contributor" to the global provision of peer review. While the country constitutes 3.3 per cent of the global research base and provides 6.6 per cent of the supply of journal articles, 7.1 per cent of all published articles are peer reviewed here, and account for 8.7 per cent of the hidden costs of peer review globally.
The report says there would be a "significant transfer" of funds to academics if peer reviewers were paid. But such a move would drive up journal prices, with the estimated "breakeven price" of a major discipline journal jumping 43 per cent, leaving libraries with a bigger bill.
"The estimated increase in the costs of subscriptions to UK libraries in the higher education sector would be of the order of £53 million, a rise of 45 per cent," the study says.
The report shows that a move to electronic-only publishing would bring a fall of about £1 billion (12 per cent) in global costs. A move towards author-pays open access publishing, on top of the cost reductions arising from a move to electronic publishing, could bring global savings of £556 million.