We present two examples in which the addition of an option market leads to sunspot equilibria despite the fact that no sunspot equilibria exist without the market. These examples highlight limitations in two prevalent views of option markets. It is often assumed that option markets help complete otherwise incomplete markets. We demonstrate that they can instead increase the number of events agents wish to insure against. As in Black and Scholes, it is often assumed that option markets are redundant. We demonstrate that an option market may not be redundant even when markets were complete before its introduction.

This paper investigates breaks in the variability and comovement of output, consumption, and investment in the G-7 economies. In contrast with most other papers on comovement, we test for changes in comovement, allowing for breaks in mean and variance. Despite claims that rising integration among these economies has increased output correlations among them, we find no clear evidence of an increase in correlation of growth rates of output, consumption, or investment. This finding is true even for the United States and Canada, which have seen a tremendous increase in bilateral trade shares, and for the euro-area members of the G-7.