Many people believe that because wages are lower in developing countries than in developed countries, competition from developing countries in goods traded internationally will soon eliminate large numbers of jobs in developed countries. Currently, developed countries' advanced technology results in higher productivity, which accounts for their higher wages. Advanced technology is being transferred ever more speedily across borders, but even with the latest technology, productivity and wages in developing countries will remain lower than in developed countries for many years because developed countries have better infrastructure and better-educated workers. When productivity in a developing country does catch up, experience suggests that wages there will rise. Some individual firms in developing countries have raised their productivity but kept their wages (which are influenced by average productivity in the country's economy) low. However, in a developing country's economy as a whole, productivity improvements in goods traded internationally are likely to cause an increase in wages. Furthermore, if wages are not allowed to rise, the value of the country's currency will appreciate, which (from the developed countries' point of view) is the equivalent of increased wages in the developing country. And although in the past a few countries have deliberately kept their currencies undervalued, that is now much harder to do in a world where capital moves more freely.

    Prior to 1965 geologists assumed that the two giant rock plates meeting at the San Andreas Fault generate heat through friction as they grind past each other, but in 1965 Henyey found that temperatures in drill holes near the fault were not as elevated as had been expected. Some geologists wondered whether the absence of friction-generated heat could be explained by the kinds of rock composing the fault. Geologists' pre-1965 assumptions concerning heat generated in the fault were based on calculations about common varieties of rocks, such as limestone and granite; but "weaker" materials, such as clays, had already been identified in samples retrieved from the fault zone. Under normal conditions, rocks composed of clay produce far less friction than do other rock types.

    In 1992 Byerlee tested whether these materials would produce friction 10 to 15 kilometers below the Earth's surface. Byerlee found that when clay samples were subjected to the thousands of atmospheres of pressure they would encounter deep inside the Earth, they produced as much friction as was produced by other rock types. The harder rocks push against each other, the hotter they become; in other words, pressure itself, not only the rocks' properties, affects frictional heating. Geologists therefore wondered whether the friction between the plates was being reduced by pockets of pressurized water within the fault that push the plates away from each other.