What are the limitations of comparative advantage theory in the field of international service trade?

Limitations of comparative advantage theory;

1, in Ricardo's trade theory, labor is the only factor of production, there is no technological progress, capital accumulation and economic development, the production scale remains unchanged, and the market structure is perfect competition. This series of assumptions can not exist at the same time, so the theory lacks a solid realistic foundation and cannot explain many contemporary international trade phenomena.

2. There is no further explanation for the difference in labor productivity.