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		| Johan  Lyhagen | 
	
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		| ''Why not use standard panel unit root test for testing PPP'' | 
	
		| ( 2008, Vol. 3 No.26 ) | 
	
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		| In this paper we show the consequences of applying a panel unit root test that assumes independence between the cross-sections when testing for a purchasing power parity relationship. The distribution of the tests investigated, including the IPS test of Im et al (2003), are influenced by a common stochastic trend which is usually not accounted for. The result is that the empirical size tends to one with the number of cross-sections. Hence, it is of crucial importance to account for this cross-sectional dependency. | 
	
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		| Keywords: | 
	
		| JEL: C2 - Single Equation Models; Single Variables: General 
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		| | Manuscript Received : Sep 19 2007 |  | Manuscript Accepted : May 14 2008 | 
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