STATA DIFFERENCE IN DIFFERENCE FREE

But, the SLA lead to a decrease in exports of SLA provinces of only 5 percent which was statistically insignificant. Their results indicate that the SLA had a significant impact on the exports of non- SLA provinces and the SLA by itself increased the exports from these provinces compared to the SLA provinces by four times. not included in the SLA because of the SLA restriction. Thus, О± 8 shows the difference in export performance of the provinces named in the SLA vs. О± 7 + О± 8 reflects the effect of the SLA contract on the provinces named in the contract. О± 7 captures the effect of the SLA agreement on the non- SLA provinces. О‘ 6 captures the difference in the mean of log exports for SLA and non- SLA provinces before the SLA restrictions came into effect. To understand why О± 8 is referred as the вЂњDifference in DifferenceвЂќ estimate, take a look at the following table which is Table 4 in the paper. The key coefficient of interest is О± 8 as it is interpreted as the causal effect of the SLA on the change in exports of the SLA provinces compared to the non- SLA provinces. SLA*Rest is an interaction term that takes the value 1 for provinces under SLA for the years SLA was in place. Rest is a dummy for the years SLA was in effect and 0 otherwise. SLA is a dummy variable which takes the value 1 for provinces on which tariffs were applied under SLA and 0 otherwise. Ex t is the US-Canada interest rate to control for price effects since exchange rates affect the relative price of Canadian lumber. R US,t is the US interest rate to control for influence of interest rates on demand for new homes (a major source of softwood lumber). Dist i is the log of distance from province I to the US border. Y it and Y US,t are the log GDP of province i and US at time t respectively to control for demand of lumber in Canada and US. Where, X it is log value of exports or log quantity of exports (annual) from province I to US. Reg X Y i Y US Dist Ex R SLA Rest SLA #Rest The regression equation they run is the following: Secondly, what was the size of the increases, if any, in the softwood lumber exports of the other provinces to the U.S. from the four provinces and if so, what was the size of the decline. Gulati and Malhotra (2006) investigated firstly, whether the SLA caused a reduction in softwood exports to the U.S. The SLA was novel since exports from only four provinces were limited and other provinces were not subject to any restriction. A tariff of $50 per thousand board feet was imposed on the next 650 million board feet exported and further exports were going to be taxed at $100 per thousand board feet.

STATA DIFFERENCE IN DIFFERENCE FREE

The first 14.7 billion board feet of softwood lumber from these provinces was exported duty free but further exports were subject to tariffs. entered into a five-year contract called the Softwood Lumber Agreement ( SLA henceforth), whereby a tariff rate quota was imposed on US-bound lumber exports from four Canadian provinces: Alberta, British Columbia, Ontario and Quebec.

Stata difference in difference