In techland, from 1980 to 2010, holding technology and human capital fixed, increasing physical capital per worker from $25,000 to $100,000 would have led to a doubling of real gdp per worker, from $40,000 to $80,000. however, not only did physical capital per worker increase from $25,000 to $100,000, but technological progress shifted the productivity curve upward so that real gdp per worker actually increased from $40,000 to $320,000. what share of the annual growth rate of real gdp per capita was attributable to increasing physical capital per worker?