Using US immigration data:  undocumented migration from Mexico to south Texas.
Jones
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RC
D000569:Americas; D002489:Central America; D003710:Demography; D019049:Developed Countries; D003906:Developing Countries; D004641:Emigration and Immigration; D007843:Latin America; D008800:Mexico; D009656:North America; D011153:Population; D011157:Population Dynamics; D013781:Texas; D014171:Transients and Migrants; D014481:United States
Americas; Central America; Demographic Factors; Developed Countries; Developing Countries; Illegal Migrants; International Migration; Latin America; Mexico; Migrants; Migration; North America; Northern America; Population; Population Dynamics; Texas; United States