1. Y/L (output per worker) exhibits continual growth.
2. K/L (capital per worker) exhibits continual growth.
3. r-δ (real interest rate) is roughly constant.
4. K/Y (capital-output ratio) is roughly constant.
5. rK/Y , wL/Y (factor shares) are roughly constant.
6. There are wide differences in the rate of growth of productivity across countries.
N. Kaldor (1961), "Capital Accumulation and Economic Growth," in F. A. Lutz and D. C. Hague, editors, The Theory of Capital. New York: St. Martin’s Press.