Social security contributions make up around one fourth of total tax revenue in OECD countries. However, there are concerns on the economic effects of high levies on labour. Recent studies suggest that at least one third of taxes on labour are shifted onto employers, leading to higher wage costs. We find substantial evidence in the literature that the nature of social security contributions matters. With a clear connection between contributions and rights, the employee will perceive this contribution as a price and not as a tax. As a consequence, these contributions will be less distortive in terms of labour supply, wage costs and private savings.