PIP: The following issues need to be examined when considering the historical links between international factor movements and international trade, and whether increases in factor flows stimulated trade or vice versa: the extent to which increased trade and factor mobility foster economic growth and development, how different factor flows are related, whether labor movements induce capital flows or vice versa, whether alternative types of factor mobility substitutes or complements, and whether trade liberalization promotes factor mobility or there are alternate types of international transactions substitutes as argued by those who ascribe to the classic Heckscher-Ohlin-Samuelson factor-price-equalization tradition. Accordingly, the historical links between international factor mobility and the extent of international trade are analyzed over the long term for Australia, Canada, and the US, high labor immigration countries; and the UK, a high labor emigration country. Time series data are used. Current international openness is assessed. International factor market integration has increased over time with trade liberalization, suggesting that traditional Heckscher-Ohlin thinking cannot be readily used to account for long-term trends in several important economies. Both trade and factor mobility have an episodic character which makes it misleading to assess current international openness only in terms of post-World War II economic trends.