研一上以前高级宏观slide jones modification

1、Jones (1995)Jones (1995)The number of scientists and engineers doing R&D in the US rose from less than 200,000 in 1950 to almost 1 million in 1989. It rose by a factor of 5. Yet TFP, our measure of A, didnt grow any faster. Its been around 2% a year for 50 years. You see the same thing in France, We

2、st Germany, and Japan: no acceleration. So Jones is contradicting Romer. Romer said in his 1986 paper that there was evidence of accelerating growth in the US and other countries in the world. But he looked at the past 3 centuries. Jones says that if you look at the past 50-100 years the pattern is

3、quite different: no acceleration. So any model that predicts it is flawed. Jones (1995)Jones (1995)So Jones proposes the following equation for the growth in knowledge: # new . ideas per A = ALA 0 01 ( is phi: fi)period research labor productivity inputSo the rate at which new ideas are discovered d

4、epends on how many researchers there are, LA, and their average productivity. Jones (1995)Lets discuss each term starting with productivity. There are three possible cases here:Cases Implication1. 0 As A “ “ (Standing on shoulders case)Here is an example of the first case: .If = -1 A = LA/AJones (19

5、95)Q: What would be an example of a discovery that actually makes it easier to come up with future discoveries (Case 3)? The microscope. Computers. Electricity perhaps. Jones refers to this as the “standing on shoulders” case, in reference to Newtons famous quote, “If I have seen farther than others

6、 it is because I was standing on the shoulders of giants.” Case 2 is the middle case where research productivity is just constant. Jones (1995)Jones: 1 or else get scale effectAlso 0) and monopoly effect: too little R&DDuplication: too much3. Bigger is better 2 countries with same A: one big (LA high) other small (LA low): big one grows faster for awhile and has permanently higher e per worker Jones (1995)Evaluation and Criticisms of Jones (1995) Model1. Ignores natural resource constraints2. Ignores quality of res