Now that the Senate is finally debating a bill that would overhaul the immigration system, legislators would do well to separate myth from reality.

Myth 1: There are more immigrants than ever and these immigrants break the mold of previous waves.

Between 1860 and 1920, fourteen percent of the population was foreign-born. The average for the 20th century is 10-plus percent. The proportion is not different today—about 13 percent. Until the 1880s immigration originated in northern and western Europe but in subsequent decades they came from southern, central and eastern Europe, which was culturally, politically and economically different. Not to mention Asians, who arrived in significant numbers.

Myth 2: Immigrants migrate because they are very poor.

The poorest people migrate internally. Rich countries such as South Korea have sent many migrants to the U.S. while Bangladeshi women, who are very poor, have migrated little even in Asia, the region with the highest rate of migration. Europe was a net exporter of people until 1980. Family ties, occupational preference, distressed conditions at home and historical ties matter. U.S. involvement in Cuba, the Philippines and the Dominican Republic in the early the 20th century was a critical factor in the movement of citizens from those countries to America. Business interests were key at various times in pushing for the legal hiring of Mexicans.

Myth 3: These immigrants are culturally different and threaten the American way of life.

Immigrants are religious, family-oriented, entrepreneurial and no more prone to crime than natives. Seventy percent of Hispanics who moved to the U.S. in the last two decades are Catholic (one fifth are “born again” Christians) and 23 percent are Protestant. One in two undocumented households has couples with children; only thirteen percent of them are headed by single parents—against one third of native households. The percentage of immigrant workers who are self-employed mirrors that of natives. Immigrant-led gentrification has revived neighborhoods from New York to Florida. Adjusted for age, the proportion of immigrants who are criminals mirrors that of natives.

Myth 4: Present-day immigrants do not assimilate, unlike previous waves.

About forty percent of newcomers speak reasonable English anyway, but the three-generation pattern echoes that of previous immigrants: the second generation is bilingual but speaks English better and the third generation speaks only English. By the third generation, out-marriage is strong among immigrants. A century ago, seventeen percent of second-generation Italian immigrants married non-Italians while 20 percent of second-generation Mexicans marry non-Hispanics today (even though, given the numbers, it is easier for them to marry another Mexican). Second-generation immigrants do better than their parents, as in the past.

Myth 5: Low-skilled workers take away jobs, lower salaries and hurt the economy.

As producers and consumers, illegal immigrants enlarge the economic pie by at least $36 billion a year. That number would triple if they were legal—various studies point to a $1 trillion impact on GDP in ten years. Low-skilled workers fulfill a need by taking jobs others do not want, letting natives move up the scale. Without them employers would need to pay higher salaries, making those products and services more expensive. They have a tiny negative effect on wages at the lowest end that is offset by a rise in the wages of those who move up—the net effect is a 1.8% rise.

Myth 6: A flexible system would mean an invasion of foreigners.

Undocumented immigration is self-regulating. When there is demand for immigrant work, they come in large numbers; in times of recession, the flow stops. Between 2005 and 2010 net immigration came down to zero. Legalizing this undocumented market would maintain the dynamic. Since the large number of undocumented people implies that legal barriers have not been very effective, it is safe to assume that market forces would be similar in a flexible system. Mexico is progressing and the problem for the U.S. will soon be how to attract more foreign labor!

Myth 7: Immigrants don’t pay taxes and cost more than they contribute.

Immigrants pay many local and state levies, including real estate and sales taxes, and about $7 billion in Social Security taxes. Between the 1970s and the 1990s they represented $25 billion more in government revenue than what they cost. They would contribute much more if they were documented. Most immigrant children have at least one parent who is a citizen, so counting all of them as part of the cost of immigration is deceptive. The welfare state was never a “pull” factor: until after World War II immigrants were not entitled to relief programs. Immigrants did not cause government spending to grow by a factor of 50 in one century.