and the discussion surrounding this fi gure in Chapter 4 that the number of scientists and engineers engaged in R&D has been growing faster than the rate of population growth in the advanced economies of the world. To take some plausible numbers, assume population growth is 1 percent and the growth rate of researchers is 3 percent per year. Assume that A # /A has been constant at about 2 percent per year.

(a) Using equation (5.6), calculate an estimate of l>(1 - f).

(b) Using this estimate and equation (5.7), calculate an estimate of the long-run steady-state growth rate of the world economy.

(c) Why does your estimate of long-run steady-state growth differ from the 2 percent rate of growth of A observed historically?

(d) Does the fact that many developing countries are starting to engage in R&D change this calculation?