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In_II 1996_MC ,_, the_AT United_JJ Nations_NN2 held_VVD its_APPGE "_" Habitat_NN1 "_" or_CC "_" City_NN1 "_" world_NN1 conference_NN1 in_II Istanbul_NP1 ._. 
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A_AT1 major_JJ issue_NN1 was_VBDZ the_AT contributions_NN2 of_IO migrant_NN1 workers_NN2 to_II cities_NN2 ,_, and_CC the_AT problems_NN2 caused_VVN by_II increasing_JJ migration_NN1 to_II the_AT world_NN1 cities_NN2 ._. 
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Some_DD believe_VV0 that_DD1 migrant_NN1 workers_NN2 make_VV0 great_JJ contributions_NN2 to_II the_AT prosperity_NN1 of_IO cities_NN2 ,_, and_CC others_NN2 claim_VV0 that_CST more_DAR migrants_NN2 to_II cities_NN2 destroy_VV0 the_AT ability_NN1 of_IO cities_NN2 to_TO sustain_VVI their_APPGE own_DA prosperity_NN1 ._. 
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Mexico_NP1 City_NN1 is_VBZ now_RT the_AT world_NN1 's_GE largest_JJT city_NN1 ,_, with_IW a_AT1 population_NN1 of_IO eighteen_MC million_NNO ._. 
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Much_DA1 of_IO the_AT growing_JJ migration_NN1 to_II the_AT Mexico_NP1 City_NN1 and_CC other_JJ world_NN1 cities_NN2 increases_VVZ their_APPGE own_DA individual_JJ prosperity_NN1 ,_, but_CCB places_VVZ serious_JJ and_CC almost_RR impossible_JJ demands_NN2 on_II the_AT city_NN1 ._. 
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Since_CS many_DA2 migrants_NN2 to_II cities_NN2 are_VBR poor_JJ ,_, they_PPHS2 often_RR require_VV0 greater_JJR social_JJ and_CC welfare_NN1 support_NN1 by_II the_AT city_NN1 ,_, and_CC the_AT city_NN1 often_RR finds_VVZ that_CST it_PPH1 is_VBZ almost_RR impossible_JJ to_TO provide_VVI all_DB of_IO the_AT health_NN1 ,_, shelter_NN1 ,_, anti-pollution_NN1 ,_, and_CC environmental_JJ requirements_NN2 that_CST this_DD1 rapid_JJ addition_NN1 of_IO migrants_NN2 causes_VVZ the_AT city_NN1 itself_PPX1 ._. 
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Thus_RR ,_, while_CS migration_NN1 to_II cities_NN2 may_VM have_VHI benefits_NN2 individually_RR and_CC to_II the_AT city_NN1 ,_, it_PPH1 is_VBZ just_RR as_RG possible_JJ for_IF there_RL to_TO be_VBI more_DAR disadvantages_NN2 than_CSN positive_JJ contributions_NN2 ._. 
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