Penn World Table Bleg
I need some help from the growth empiricists out there. If you aren't one of them, stop reading. Continuing will be a waste of your time.
For researchers studying economic growth, one of the standard resources for cross-country data has been the Penn World Table. My 1992 paper with David Romer and David Weil (my most cited paper by a large margin) used this resource, as have numerous other papers in this literature. In my intermediate macro book, I present a couple of figures presenting some of these data.
Here's the problem: It seems that the data have changed substantially in the most recent revision, and I cannot figure out why.
My intermediate macro text shows a scatterplot of per capita income and the investment share of GDP. These two variables are strongly positively correlated. When revising this figure with the newest data, I found that the correlation declines substantially (though is still positive). When I looked into the source of the change, I found that the historical estimates of the investment share of GDP have changed, in some some cases by a lot.
Let me give you an example. Take the investment share for Ghana in the year 2000. According to version 6.2 of the data, the investment share was about 5 percent. In version 7.0, it was about 21 percent. This is one of the larger changes I have found, but it is not the only country for which there are sizable changes in the reported investment share of GDP.
I understand that the changes may be related to new information about the relative price of investment goods. But the changes seem too large to be explained so easily, although perhaps I am wrong about this. If anyone can shed light on the matter, I would be greatly appreciative. Send me an email if you can help.
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Update: I have not yet fully figured this out, but readers have sent me some useful links. If you are interested, click here, here, and here.
For researchers studying economic growth, one of the standard resources for cross-country data has been the Penn World Table. My 1992 paper with David Romer and David Weil (my most cited paper by a large margin) used this resource, as have numerous other papers in this literature. In my intermediate macro book, I present a couple of figures presenting some of these data.
Here's the problem: It seems that the data have changed substantially in the most recent revision, and I cannot figure out why.
My intermediate macro text shows a scatterplot of per capita income and the investment share of GDP. These two variables are strongly positively correlated. When revising this figure with the newest data, I found that the correlation declines substantially (though is still positive). When I looked into the source of the change, I found that the historical estimates of the investment share of GDP have changed, in some some cases by a lot.
Let me give you an example. Take the investment share for Ghana in the year 2000. According to version 6.2 of the data, the investment share was about 5 percent. In version 7.0, it was about 21 percent. This is one of the larger changes I have found, but it is not the only country for which there are sizable changes in the reported investment share of GDP.
I understand that the changes may be related to new information about the relative price of investment goods. But the changes seem too large to be explained so easily, although perhaps I am wrong about this. If anyone can shed light on the matter, I would be greatly appreciative. Send me an email if you can help.
-----
Update: I have not yet fully figured this out, but readers have sent me some useful links. If you are interested, click here, here, and here.
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