Different countries' methods or definitions for categorizing their people is evidence for how race is a social construct—it exists based on societal definitions. Information on census data across the globe shows that different countries categorize people by race, ethnicity, national origin, or ancestry. At the same time, such terms may have different meanings across countries. What one country defines as "race" may be "ethnicity" in another country. An example of different countries' racial definitions can be seen in comparing Brazil and the United States' racial categories. The United States's racial categories are mainly based on ancestry while Brazil's racial categories are based on outward appearance. Just as racial categories vary between place, racial categories have shifted over time. In the United States alone, racial categories changed over time and new racial categories were added as immigrants from Europe and Asia entered the country. Today, Irish Americans are considered White. Yet, in the 1900s, Irish and other southern and eastern European immigrants were considered "ethnics" and not White. Shifting categories and definitions of race over time is further evidence that race is not biologically or naturally fixed but societally determined.