Social Security and the Interactions Between Aggregate and Idiosyncratic Risk

By Daniel Harenberg and Alexander Ludwig

We ask whether a PAYG-financed social security system is welfare improving in an economy with idiosyncratic and aggregate risk. We argue that interactions between the two risks are important for this question. One is a direct interaction in the form of a countercyclical variance of idiosyncratic income risk. The other indirectly emerges over a household’s life-cycle because retirement savings contain the history of idiosyncratic and aggregate shocks. We show that this leads to risk interactions, even when risks are statistically independent. In our quantitative analysis, we find that introducing social security with a contribution rate of two percent leads to welfare gains of 2.2% of lifetime consumption in expectation, despite substantial crowding out of capital. This welfare gain stands in contrast to the welfare losses documented in the previous literature, which studies one risk in isolation. We show that jointly modeling both risks is crucial: 60% of the welfare benefits from insurance result from the interactions of risks.

This is an interesting paper that highlights that an important benefit of a social security system is not only coming from the insurance against lifecycle income risk, individual or aggregate, but majorly from the interaction of such indvidual and aggregate risks. And this paper does not even consider the advantage of insuring against longevity risk.


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