Without years of activities by trade unions to promote occupational health and safety, workplaces today would be much more dangerous. So limiting the ability of workers to form trade unions might make society as a whole worse off.

These are the central conclusions of a study by Professors Alejandro Donado and Klaus Wälde, which challenges the widespread view among economists that unions often damage society by causing higher rates of unemployment.

Their research, published in the September 2012 issue of the Economic Journal, suggests that workers'' movements – joint collective actions by individuals – are needed to raise political awareness, to lobby for changes in working conditions and eventually to bring about regulatory changes that require better safety measures. In this sense, the authors argue, trade unions are able to increase the welfare of society.

The standard economic argument about trade unions is that by demanding higher wages, they reduce firms'' incentives to create jobs. Because of this, they usually enjoy a bad reputation among economists, with many even demanding tighter restrictions on workers forming trade unions.

But as this new study shows, the impact that trade unions have had on improving safety measures has been crucial. Take the example of the black lung disease, an illness caused by the repeated and yearlong inhalation of small amounts of coal dust. There was a particularly high risk that you might develop this disorder if you worked underground, particularly as a coal miner.

A potential causal link between the occupation of coal miner and the illness was first made by a physician as early as 1831. But it took another 130 years and many more cases of illness, protests, strikes, investigations and examinations for a law officially accepting this connection to be introduced in the United States.

Similar examples of the effectiveness of coordinated action in getting illnesses recognised as occupational illnesses through what were essentially workers'' movements can be cited in the agricultural sector, the ceramics industry and the automotive industry, to name but a few.

The current debate on whether ''burnout'' and other stress-related symptoms should be considered as occupational illnesses shows how topical the subject still is today.

The researchers note that it is often impossible for a worker alone to determine whether a particular illness should be attributed to personal predisposition (that is, to inherited traits and/or lifestyle) or whether the occupational environment is to blame. The major advantage of a group – for example, in the form of a trade union – is its ability to gather information from a large number of different individual cases.

If a sufficiently large number of miners fall ill with the black lung disease, it is much more difficult to disprove a causal connection than if there are only one or two individual cases. This advantage with regard to the availability of information, together with their increased political impact as a group, enable trade unions to intervene in the political process to ensure that improved occupational health and safety provisions are put in place at work.

In more general terms, Donado and Wälde observe that the side effects caused by new ways of production reveal themselves only gradually. While there might be uncertainty about the health implications of a certain job, initially there is often ignorance about the implications, sometimes just the absence of any doubt.

When workers then start sensing that ''something is going wrong'' (that work conditions are causing health problems), these claims are often met with doubt, not only by employers but also by insurance companies and even the government.

''How Trade Unions Increase Welfare'' by Alejandro Donado and Klaus Wälde is published in the September 2012 issue of the Economic Journal.