“…In accordance with Quah and Crowley (2010 [10], 2012 [11]) and Quah (2012 [12-14], 2013 [15], 2014 [16][17][18], 2015 [19]) the OCA criteria investigated in this paper are trade openness, business cycle synchronization, real exchange rate variability, inflation convergence, and real interest rate symmetry. Similar metrics have been used by Artis and Zhang (2001 [20], 2002 [21]), of which the efficacy of the criteria was evidenced when Portugal, Italy, Greece, and Spain were selected as the group that possesses the least parallel OCA features against Germany.…”