The degree of openness to commercial trade of goods and services is also an important consideration with regard to the exchange rate system, both how it has developed and where it is going. As with capital flows, emerging market participation in global trade has risen exponentially in the last two decades. The average share of external trade (measured by exports plus imports, divided by two) in GDP for emerging market countries rose from about 30% in the late 1960s to 40% in the late 1990s. Within this, the trend towards opening up to trade has been particularly marked in Asia. As trade makes up an increasingly large share of emerging market GDP, so changes in the exchange rate and in output and prices are increasingly interrelated. At the same time, the type of trade has changed significantly, moving away from a dependence on commodities towards manufacturing. This change appears to have helped stabilize the terms of trade of emerging market economies, as manufacturing prices change considerably more slowly than do commodities. However, it has also made the economy as a whole more sensitive to exchange rate fluctuations. Commodities are priced in US dollars and fluctuate for the most part independently of fluctuations in exchange rates. Conversely, supply and demand of manufactured trade is very sensitive to exchange rate fluctuations.