NATIONAL BUREAU OF ECONOMIC RESEARCH
NATIONAL BUREAU OF ECONOMIC RESEARCH

NBER Working Papers by Haroon Mumtaz

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Working Papers

October 2009One TV, One Price?
with Jean Imbs, Morten O. Ravn, Hélène Rey: w15418
We use a unique dataset on television prices across European countries and regions to investigate the sources of differences in price levels. Our findings are as follows: (i) Quality is a crucial determinant of price differences. Even in an integrated economic zone as Europe, rich economies tend to consume higher quality goods. This effect accounts for the lion’s share of international price dispersion. (ii) Sizable international price differentials subsist even for the same television sets. The average bilateral price difference is as high as 80 euros, or 8% of the average TV price in our sample. (iii) EMU countries display lower price dispersion than non-EMU countries. (iv) absolute price differentials and relative price volatility are positively correlated with exchange rate volatility,...
September 2005"Aggregation Bias" DOES Explain the PPP Puzzle
with Jean Imbs, Morten O. Ravn, Hélène Rey: w11607
This article summarizes our views on the role of an "aggregation bias" in explaining the PPP Puzzle, in response to the several papers recently written in reaction to our initial contribution. We discuss in particular the criticisms of Imbs, Mumtaz, Ravn and Rey (2002) presented in Chen and Engel (2005). We show that their contentions are based on: (i) analytical counter-examples which are not empirically relevant; (ii) simulation results minimizing the extent of "aggregation bias"; (iii) unfounded claims on the impact of measurement errors on our results; and (iv) problematic implementation of small-sample bias corrections. We conclude, as in our original paper, that "aggregation bias" goes a long way towards explaining the PPP puzzle.
December 2002PPP Strikes Back: Aggregation and the Real Exchange Rate
with Jean Imbs, Morton O. Ravn, Helene Rey: w9372
We show the importance of a dynamic aggregation bias in accounting for the PPP puzzle. We prove that established time series and panel methods substantially exaggerate the persistence of real exchange rates because of heterogeneity in the dynamics of disaggregated relative prices. When heterogeneity is properly taken into account, estimates of the real exchange rate half-life fall dramatically, to little more than one year, or significantly below Rogoff's consensus view' of three to five years. We show corrected estimates are consistent with plausible nominal rigidities, thus, arguably, solving the puzzle. We also explain why traded goods prices account for the bulk of the persistence and volatility of the real exchange rate. The reason is that traded goods prices display dynamics that ar...

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