Similarly to Mestizo and indigenous peoples, estimates of the percentage of European-descended Mexicans vary considerably depending on the criteria used: recent nationwide field surveys that account for different phenotypical traits (hair color, skin color etc.) report a percentage between 18%-23% if the criterion is the presence of blond hair, and of 47% if the criterion is skin color, with the later surveys having been conducted by Mexico's government itself. While, during the colonial era, most of the European migration into Mexico was Spanish, in the 19th and 20th centuries, a substantial number of non-Spanish Europeans immigrated to the country, with Europeans often being the most numerous ethnic group in colonial Mexican cities. Nowadays, Mexico's northern and western regions have the highest percentages of European populations, with the majority of the people not having native admixture or being of predominantly European ancestry.