Hans-Werner Sinn (born 7 March 1948) is a German economist who served as President of the Ifo Institute for Economic Research from 1999 to 2016.

The Dutch Economist and former State Secretary of Education, Science and Culture of the Netherlands Rick van Ploeg honored Sinn's contribution to strengthening Economics as a subject in Germany and continental Europe.

[15] In a study by Ursprung and Zimmer,[16] based on SSCI citations per author of the full oeuvre, Sinn ranked second of all German economists, after Nobel laureate Reinhard Selten.

[19] In its latest evaluation of the Ifo Institute, the Leibniz Association praised Sinn as one of "Germany’s most renowned economists, who constantly succeeds in bringing the most varied economic issues to public debate".

Since 1989 Sinn has served on the Advisory Council of the German Ministry of Economics, and represented the Free State of Bavaria on the Board of Supervisors of HypoVereinsbank for ten years.

With the exception of his diploma dissertation, also published in a journal, on the Marxian Law of the tendencial decline of the rate of profit,[26] Sinn dealt in his early years particularly with economic risk theory.

He made a name for himself with his dissertation "Ökonomische Entscheidungen bei Ungewissheit" (1980), published in English as "Economic Decisions under Uncertainty" (1983), with numerous spin-off articles.

Subsequent work focused on the axiomatic basis of mean-variance analysis, on the foundation of the principle of insufficient reason, on the psychological foundation of risk preference functions and on the analysis of risk decisions under limited liability, which he subsequently developed into a theory of bank regulation in his Yrjö Jahnsson Lectures, "The New Systems Competition".

With his dissertation in 1977 on excess risk propensity under liability restrictions, Sinn, in the opinion of Martin Hellwig, preceded the pioneering analysis of Stiglitz and Weiss of 1981.

[31][32][33][34] His study on the stimulating effects of accelerated depreciation and the various components of capital income taxation on intertemporal, international, and intersectoral allocation is still considered one of the standard works in this field.

[36] Here, with the help of present-value equivalents, he showed that the low returns from statutory pension insurance based on the pay-as-you-go method has only an apparent efficiency disadvantage in comparison to a capitally funded procedure.

His "green paradox" states that environmental policies that promote substitute technologies over time with increasing intensity (and in the process lower the prices for fossil fuels relative to the values they otherwise would have obtained) will induce the resource suppliers to accelerate extraction, thus contributing to global warming.

In 2005 he was one of the first German economists to sign the "Hamburger Appell", which argued for fundamental supply-side reforms and rejected demand-oriented concepts of economic policy.

At the expense of the domestic sectors, Germany has inflated value added in exports too strongly and at the same time has placed too much emphasis on the final stages of production.

In addition the lack of personal liability for homeowners created in a similar way an exaggerated willingness to take risks and thus caused the United States housing bubble.

To correct this situation Sinn has called for considerably higher capital reserve requirements, the balancing of offshore business and a return to the accounting principle of the lower of cost of the German Commercial Code (HGB).

[38] Against the background of the Great Recession, Sinn advocates a return to the tradition of ordoliberalism and of ordoliberal economists like Walter Eucken, Alfred Müller-Armack, Alexander Rüstow, and Ludwig Erhard, who argued a strong state should provide a framework or economic order inside which market forces and free market competition can develop.

[41] Sinn accuses the Greens of pursuing environmental protection policies with unsuitable means and of ignoring the economic laws of the European emissions trading system as well as the worldwide market for fossil fuel.

He also favours employing a withholding tax on the yields of financial investments to curb the desire of the resource providers to extract more fossil fuels.

[50] In July 2012, Sinn was one of the eventually more than 270 signatories of an open letter written by Walter Krämer of the Technical University of Dortmund against Chancellor Angela Merkel’s Brussels agreement on direct recapitalization for ailing European banks.

The "momentous tiff", as The Economist dubbed it, has in the meantime become more nuanced, with Krämer and Sinn publishing a more muted version in which they endorsed a banking union based on the bail-in principle.

Sinn joined Heinemann and Krämer in publishing a joint appeal on the issue in Plenum der Ökonomen, an internet forum of German professional economists.

[53] A study in 2007 placed Sinn, in terms of number of citations in scientific journals, second to German Nobel laureate Reinhard Selten.