Abstract: Most popular explanations of the happiness paradox cannot fully account for the lack of growth in U.S. reported well-being during the last thirty years (Blanchflower and Oswald (2004)). In this paper we test an alternative hypothesis, namely that the decline in U.S. social capital is responsible for what is left unexplained by previous research. We provide three main findings. First, we show that the inclusion of social capital does improve the account* *of reported happiness. Second, we provide evidence of a decline in social capital indicators for the period 1975-2004, confirming Putnam's claim (Putnam (2000)). Finally, we show that failed growth of happiness* *is largely due to the decline of social capital and, in particular, to the decline of its relational and intrinsically motivated component.