The difference between race and ethnicity is that the former affects more on biological factors, while the second refers to aspects of cultural. Race and ethnicity may coincide, but have different dimensions. From the 60s and 70s, the combined action of three types of factors began to seriously question the different forms of assimilationist paradigm. On the one hand, the demands and social dynamics generated by minority groups, national minorities in some cases, ethnocultural from immigrant groups in others. On the other, the difficulties and growing problems in the process of social integration of immigrants associated, among other factors, to the phenomena of duality and the decline of traditional industrial society. Last but not least,
