We offer an alternative explanation for the decline in labor force participation of senior workers. Typically, tax and transfer explanations have been proposed. On the contrary, a model with imperfectly competitive labor market allows to consider as well the effects of a drop in bargaining power, which would not be possible in a purely neoclassical framework. We find that a decline in the bargaining power of workers, which has taken place in the last four decades, has largely contributed to the rise in inactivity in Europe. However, we need a combination of these two explanations, along with population aging and a fall in the matching efficiency, in order to correctly reproduce the joint evolutions of other labor market variables such as the employment and unemployment rates
