In: Economics
Consider the following data on real GDP per capita in:
Year |
Per Capita Real GDP |
1950 |
14 339 |
1960 |
17 351 |
1970 |
23 790 |
1980 |
30 732 |
1990 |
35 868 |
2000 |
43 288 |
2010 |
46 406 |
2011 |
47 554 |
2012 |
47 741 |
2013 |
48 066 |
2014 |
48 780 |
a) Calculate the percentage growth rates in real GDP per capita in each of the years 2011 through 2014, from the previous year.
b) Now, instead of calculating the annual percentage growth rates in the years 2011 through 2014 directly, use as an approximation
100×logyt-logyt-1
where yt is real per capita GDP in year t. How close does this approximation come to the actual growth rates you calculated in part (a)?
a)
The annual percentage growth rates in real GDP per capita is given by [(Yt - Yt-1)/Yt-1]*100%
Thus, the annual percentage growth rates in real GDP per capita for each of the years 2011 through 2014, from the previous year is:
Year | Per Capita Real GDP | The percentage growth rates in real GDP per capita |
1950 | 14339 | |
1960 | 17351 | |
1970 | 23790 | |
1980 | 30732 | |
1990 | 35868 | |
2000 | 43288 | |
2010 | 46406 | |
2011 | 47554 | 2.47% |
2012 | 47741 | 0.39% |
2013 | 48066 | 0.68% |
2014 | 48780 | 1.49% |
b)
Using as an approximation 100×logyt-logyt-1, where yt is real per capita GDP in year t, the result is:
Year | Per Capita Real GDP (Yt) | The percentage growth rates in real GDP per capita | Per Capita Real GDP (Yt-1) | 100×logyt-logyt-1 |
1950 | 14339 | |||
1960 | 17351 | 14339 | ||
1970 | 23790 | 17351 | ||
1980 | 30732 | 23790 | ||
1990 | 35868 | 30732 | ||
2000 | 43288 | 35868 | ||
2010 | 46406 | 43288 | ||
2011 | 47554 | 2.47 | 46406 | 1.06 |
2012 | 47741 | 0.39 | 47554 | 0.17 |
2013 | 48066 | 0.68 | 47741 | 0.29 |
2014 | 48780 | 1.49 | 48066 | 0.64 |
It shall be noted that when 100×logyt-logyt-1 is used as an approximation, the result is not close to the annual percentage growth rates in real GDP per capita. This is because, the approximation uses log, which is log to the base of 10.
It shall be noted that instead natural log, that is log to the base of e if used, the approximation would take the form
100×lnyt-lnyt-1
The result is:
Year | Per Capita Real GDP (Yt) | The percentage growth rates in real GDP per capita | Per Capita Real GDP (Yt-1) | 100×logyt-logyt-1 | 100×lnyt-lnyt-1 |
1950 | 14339 | ||||
1960 | 17351 | 14339 | |||
1970 | 23790 | 17351 | |||
1980 | 30732 | 23790 | |||
1990 | 35868 | 30732 | |||
2000 | 43288 | 35868 | |||
2010 | 46406 | 43288 | |||
2011 | 47554 | 2.47 | 46406 | 1.06 | 2.44 |
2012 | 47741 | 0.39 | 47554 | 0.17 | 0.39 |
2013 | 48066 | 0.68 | 47741 | 0.29 | 0.68 |
2014 | 48780 | 1.49 | 48066 | 0.64 | 1.47 |
It shall be noted that excel function log(yt) would provide the value of log to the base of 10, whereas Ln(yt) would provide the value of log to the base of e
Thus, the approximation 100×lnyt-lnyt-1 provides an estimate that is close to the annual percentage growth rates in real GDP per capita