Friday, October 23, 2009

Ouch!

A new NBER working paper by Johnson, Larson, Papageorgiou, and Subramanian (ungated version available here, click on working papers and it's the first one) has a few bones to pick with the Penn World Tables:

This paper sheds light on two problems in the Penn World Table (PWT) GDP estimates. First, we show that these estimates vary substantially across different versions of the PWT despite being derived from very similar underlying data and using almost identical methodologies; that this variability is systematic; and that it is intrinsic to the methodology deployed by the PWT to estimate growth rates. Moreover, this variability matters for the cross-country growth literature.

While growth studies that use low frequency data remain robust to data revisions, studies that
use annual data are less robust. Second, the PWT methodology leads to GDP estimates that are not valued at purchasing power parity (PPP) prices. This is surprising because the raison d’être of the PWT is to adjust national estimates of GDP by valuing output at common international (purchasing power parity [PPP]) prices so that the resulting PPP-adjusted estimates of GDP are comparable across countries.

Wow, I hope 5 year averages count as "low frequency data"!

3 comments:

Gabriel said...

"GDP", "services"... what is that? Nobody believes it anyway.

Theory ahead of measurement?

Tom said...

"this variability is systematic; and that it is intrinsic to the methodology..."

Systematic?
"Characterized by order and planning"

-or-

systemic
"of or pertaining to a system."

Somehow I doubt that "variability" is "characterized by order and planning."

Yes, I am easily distracted.

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