identifying regional industrial clusters in imperial county california prepared for the center border and economic studies sergio j rey principal investigator department of geography san diego state university ca 92182 may 2003 contents 1 introduction 2 preliminary consensus output screening 3 selection candidate industries defining screened 5 dendrogram trimming 8 9 employment 12 17 19 vs 20 4 characteristics 22 cluster size 25 wage rates 28 value added 30 linkages 31 internal external 33 multipliers 34