1. Population,Technology,and Growth:From Malthusian Stagnation to the Demographic Transition and Beyond By Oded Galor and David N. Weil Presented by Lv Dan

2. Historical evidence Malthusian regime Post- Malthusian regime Modern Growth regime Technological progress slowrisegrow Population growth Slowrisereduce Income per capita constantgrow Historical evolution of population growth, technological change and the standard of living

4. The transition between three distinct regimes In the Malthusian and the Post-Malthusian Regime there is a positive relationship between the level of output per capita and the growth rate of population,while in the Modern Growth Regime the relationship is negative. The key event separates the M and PM: The acceleration in the space of technological progress The key event separates the PM and Modern: The demographic transition that followed the industrial revolution

5. Objectives and Contributions This paper develops a unified endogenous growth model in which the evolution of population,technology,and output growth is largely consistent with the process of development in the human history.

6. The Model Key point Technological progress raises the rate of return to human capital(and why), and thus induces the substitution of quality of children for quantity. The production of human capital: The education level of children affects the speed of technological progress. The speed of technological progress is also a positive function of the overall size of the population. The technological progress:

7. Production The economy is characterized by the existence of a fixed factor of production, land, and a subsistence level of consumption. The output produced at time t: Output per worker produced at time t: The wage per efficiency unit of labor :

8. Preference The utility function Is the number of children of individual t, is the level of human capital of each child and is the wage per efficiency unit of labor at time t+1

9. Budget Constraint the time cost for a member of generation t of raising a child with a level of education is: The budget constraint :

10. Optimization s.t F.O.C ( ):

12. The optimization with respect to The optimal level of education

13. The optimal number of children:

15. The evolution of effective resources per worker:

16. The dynamical system The first regime : The second regime :

17. The evolution of technology and education

20. Explain the result Malthusian regime In early stages,, population is low enough that the implied rate of technological change is very small. parents have no incentives to provide education. (figure 3) is constant technological change is very small,and brings about proportional increase in output and population.

21. Post-Malthusian Regime, the increase in the size of population over time causes the intensified pace of technological change.(figure 4 shows multiple, history dependent SS, jump need stochastic shock) At a certain level of population, we get figure 5, parents find optimal to provide education. Increases in the g and e feed back on each other.

22. Still positive relationship between population and income per capita substitute effect: technological change induces the substitution of quality for quantity. income effect:technological change raises potential income, thus increases the fraction of the time that devote to raising children. The income effect dominates, and the population growth rate increases.

23. The demographic transition and Modern Growth regime Output increases and the subsistence consumption constrain is no longer binding. The total amount of time is constant. g continue to raise the education, population growth will fall.

24. Concluding Remarks A single unified model will improve the understanding of the underlying phenomena and generate superior testable predictions and more accurate analysis of the effects of policy interventions. Differences in the ability to escape the M trap and in the speed of takeoff: differences between countries in the determination of population growth or in the process of technological change as a result of institution and cultural factors. Not fully applicable to currently developing countries