As Triple A points out
. . . analysing the terms of trade is not a simple matter. Prices of imports and exports will constantly be changing according to supply and demand and the average changes in these prices will show up in the terms of trade. An improvement in the terms of trade may well be good news for exporters, but are they perhaps less competitive in the medium term as a result?
This article outlines the complexity of trade statistics and efforts by policy makers to interpret these results.