Parsley and Wei (1996) look for convergence towards the LOP in the absence of
trade barriers or nominal exchange rate fluctuations by analyzing a panel of 51
prices from 48 cities in the United States. They find convergence rates substantially
higher than typically found in cross-country data, that convergence occurs
faster for larger price differences and that rates of convergence are slower for
cities farther apart. Extending this line of research, Engel and Rogers (1996) use
CPI data for both U.S. and Canadian cities and for 14 categories of consumer
prices in order to analyze the stochastic properties of deviations from the LOP.
The authors provide evidence that the distance between cities can explain a
considerable amount of the price differential of similar goods in different cities
of the same country. Nevertheless, the price differentials are considerably larger
for two cities across different countries relative to two equidistant cities in the
same country. The estimates of Engel and Rogers suggest that crossing the
national border—the so-called “border effect”—increases the volatility of price
differentials by the same order of magnitude that would be generated by the addition
of 2,500 to 23,000 extra miles between the cities considered. Rogers and
Jenkins (1995) find similar results to Engel (1993), providing evidence that the
“border effect’’ is effective in increasing not only the volatility of price differentials
but also their persistence.