Why do Indian-Americans earn more than other ethnic groups in the US?
First of all, this is a substantially true proposition:
According to the latest US Census data, the Indians now have an
average household earning of $123,700. . . . The median earnings of
the Indians there is nearly double the nationwide average of $63,922.
(The quoted material and chart are from the Hindustan Times). Wikipedia corroborates this conclusion.
This is mostly because Indian-Americans in the United States are primarily recent immigrants who obtained visas to allow them to immigrate based upon work related visas for highly skilled and high paying information technology, science, engineering, and medical jobs, or their children who have followed in their parents footsteps.
For example, "Indians form the second largest group of physicians after non-Hispanic Caucasian Americans (3.9%) as of the 1990 survey, and the percentage of Indian physicians rose to around 6% in 2005."
This pattern of immigration explains why "in 2015, of Indian Americans aged 25 and older, 72% had obtained a bachelor's degree and 40% had obtained a postgraduate degree, whereas of all Americans, 19% had obtained a bachelor's degree and 11% had obtained a postgraduate degree." (from the same source citing this ultimate source).
The fact that Indian Americans are mostly recent immigrants is demonstrated by the explosive growth of this population in the United States:
More than two-thirds of Indian Americans have lived in the United States for less than twenty-five years, and more than 80% of Indian Americans have lived in the United States for less than thirty-five years. A fairly modest share of Indian Americans are highly assimilated descendants of immigrants who were born in the U.S.
Also, about a quarter of Indian Americans live in the high income New York City metropolitan area, where the high cost of living requires high incomes to obtain workers in a competitive manner with other areas where the cost of living is lower. A large share of the rest live in other high wage, high cost of living areas such as metropolitan Washington D.C. and major metropolitan areas in California.
Put another way, other countries also have immigrants of the kind that have come to the U.S. from India, but these are diluted by other forms of immigration.
In contrast, because there were very few Indian Americans in the United States until recently, there were few options for them to have family based immigration. (Most Indian American family immigration involves marriage to someone in the U.S. in a relationship that started while the Indian American was on a student visa as a college or graduate student in the U.S., or while the Indian American was on a temporary highly skilled worker H1-B visa, or a marriage of an Indian American high income tech or medical sector worker already in the U.S. permanently to someone from India.) And, because Indian Americans all live in one country with a very large population, instead of being fragmented among many smaller countries, its modest rate of immigration by other means bars people in India from using the "immigration lottery" in the U.S. immigration system to migrate to the U.S.
So, work and investment based immigration is the only option for immigration to the U.S. from India. The predominance of forms of immigration available only to high wage earners in the mix of Indian American immigrants (and the lack of "reversion to the mean" by the descendants of immigrants in the U.S. since not many of them have entered the work force in their own right yet), has driven up the average wages of Indian Americans.
Immigrant populations are almost never representative samples of the people in their homelands.
This divergence is easy to achieve because there are about 50,000 Indian American immigrants a year in recent years to the United States, but the population of India is more than 1.4 billion. Only about one in 28,000 people in Indian emigrate to the U.S. each year.
In the same vein recent immigrants from Nigeria have above average education and income, relative to native born Americans, for much the same reasons (they are also not eligible for the immigration lottery since even low levels of immigration from the country of 225 million people disqualify Nigerians from it, and they have few opportunities for family based immigration since 20th-21st century immigration from Nigeria has also seen recent explosive growth), despite emigrating from a country that as a whole is much less affluent and less well educated country than the U.S.
Another example of immigrant populations almost never being representative samples of the people in their homelands is that it is disproportionately true in most cases that immigrants adhere to religious beliefs that are minority religious beliefs in their homelands.
For example, the immigrants from predominantly Muslim countries and East Asian countries are much more likely to be Christians than members of their homelands in general, and immigrants from Latin America are much more likely to be Protestants than people in Latin America generally.