Appendix 6 183 



variables. The time variable is different here from that used in the 

 text. In appendix table 6.B the time coefficient is common to all 

 countries, while in the text a country-specific time variable is in- 

 cluded. The inclusion of the country coefficient in regression 3 

 improved the time coefficients; the estimates of this variable in 

 regression 2 imply that productivity increased from 1955 to 1960 

 (set to zero), decreased in 1965, and rose again in 1968. Regression 

 3 shows productivity constantly increasing with time. 



