In 2000, a genetically modified corn variety called StarLink that was not approved for human consumption was discovered in the food-corn supply. To estimate the price impact of this event on the U.S. corn market, we develop the relative price of a substitute method. This method applies not only to the StarLink event but also to rare events in other markets. We find that the contamination led to a 6.8% discount in corn prices and that the suppression of prices lasted for at least a year.

In 1978, California adopted building codes designed to reduce the energy used for temperature control. Using a rich data set of hourly electricity consumption for 158,112 houses in Sacramento, we estimate that the average house built just after 1978 uses 8% to 13% less electricity for cooling than a similar house built just before 1978. Comparing the estimated savings to the policy's projected cost, our results suggest the policy passes a cost-benefit test. In settings where market failures prevent energy costs from being completely passed through to home prices, building codes can serve as a cost- effective tool for improving energy efficiency.

This paper bridges the gap between processes where shocks are permanent and those with transitory shocks by formulating a process in which the long-run impact of each innovation is time-varying and stochastic. In the stochastic permanent breaks (STOPBREAK) process, frequent transitory shocks are supplemented by occasional permanent shifts. Consistency and asymptotic normality of quasi-maximum-likelihood estimates is established, and locally best hypothesis tests of the null of a random walk are developed. The model is applied to relative prices of pairs of stocks and significant test statistics result.