How serious is the omission of bilateral tariff rates in gravity?

In this paper, using the worldwide dataset of bilateral tariff rates, we explore how serious the omission of bilateral tariff rates in gravity is. Our findings are as follow. Firstly, the omission of bilateral tariff rates seems not to be so serious in terms of omitted-variable biases because the coefficients for the usual gravity variables do not change before or after their inclusion. Secondly, while the widely-used dummy variable of regional trade agreement could not play an alternative role in place of tariff rates, the inclusion of time-invariant pair fixed effects in addition to the time-variant importer fixed effects and exporter fixed effects accounts for the omission of tariff rates. The inclusion of those fixed effects makes the coefficient for bilateral tariff rates insignificant.

Gravity with multiple tariff schemes

This study contributes to the literature on gravity analysis by explicitly incorporating both most favored nation (MFN) rates and regional trade agreement (RTA) rates. Our gravity equation considers the fact that all exporters do not necessarily utilize RTA schemes, even when exporting to their RTA partners. We apply the tariff line–level data on worldwide trade to this gravity equation. As a result, we find a significantly negative coefficient for the (log) ratio of RTA rates to MFN rates. From the quantitative point of view, we show that in the first year of the Japan–Australia Economic Partnership (i.e., 2015), exports from Australia to Japan are expected to increase by 6% compared with the exports in 2014. Furthermore, it is shown that, based on the subsequent reduction in RTA rates, the magnitude of the trade-creation effect through tariff reductions gradually rises over time.