The value index , unit value index and quantum index measure the changes in value , prices and volume of external merchandise trade respectively . as from june 2002 , the merchandise trade index numbers have been updated 貨值指數(shù)、單位價格指數(shù)及貨量指數(shù)分別量度對外商品貿(mào)易貨值、貨品價格及貨量的變動。