This indicates, for example, that an increase in import penetration from 0 to 50% would reduce the ratio of price to marginal cost by 12%. She also finds that reduced tariffs are associated with lower price-cost ratios, but that result is only significant at the 15% level.
The most popular models for forecasting volatility are the GARCH (generalized autoregressive conditional heteroscedasticity) family. Dozens of variations of GARCH models have been proposed for forecasting volatility based on the assumption that returns are generated by a random process with time-varying and mean- reverting volatility (Alexander, 2001, p.
This is typically the case when parameters later in the list are dependent on specific values of variables earlier in the list.