-- Immigrants across the U.S. are refusing to go to work, attend school and shop today as part of the Day Without Immigrants, a series of protests intended to illustrate the significant economic and social impact that immigrants have on the country.
Hundreds of business owners in Washington, D.C.; Austin, Texas; Boston; Philadelphia; and other cities are participating in the protests.
"I want to make sure that immigrants, such as myself and others, don’t live in fear," said Andy Shallal, an Iraqi-American entrepreneur best known for his D.C.-area restaurant, bookstore and performance venue chain Busboys and Poets.
"There are times when standing on the sidelines is not an option," he said. "This is one of those times."
While the economic impact of today's actions remains unclear, several economic experts told ABC News that the U.S. economy and workforce would be a "disaster" without immigrants.
"Immigrants are overrepresented in a lot of occupations in both low- and high-skilled jobs," he explained. "You'd feel an impact and loss in many, many different occupations and industries, from construction and landscape to finance and IT."
Though some U.S.-born workers could fill some of those jobs, large gaps in several sectors would remain and cause a decline in the economy, Costa said.
Immigrants earned $1.3 trillion and contributed $105 billion in state and local taxes and nearly $224 billion in federal taxes in 2014, according to the Partnership for a New American Economy, based on an analysis of the U.S. Census Bureau's latest American Community Survey. The partnership is a group of 500 Republican, Democratic and independent mayors and business leaders who support immigration reforms that create jobs for Americans, according to its site.
In 2014 immigrants had almost $927 billion in consumer spending power, an analysis of the survey showed.
"Immigrants are a very vital part of what makes the U.S. economy work," said Jeremy Robbins, the executive director of the Partnership for a New American Economy. "They help drive every single sector and industry in this economy."
He added that without immigrants, there would be fewer businesses and and inventions.
Though immigrants make up about 13 percent of the U.S. population, they contribute nearly 15 percent of the country's economic output, according to a 2014 report from the Economic Policy Institute. The report contains the institute's latest data on immigration and the U.S. economy.
"Immigrants have an outsized role in U.S. economic output because they are disproportionately likely to be working and are concentrated among prime working ages," the EPI report says. "Moreover, many immigrants are business owners. In fact, the share of immigrant workers who own small businesses is slightly higher than the comparable share among U.S.-born workers."
David Kallick, the director of the Immigration Research Initiative at the Fiscal Policy Institute, said Americans should not be fearful that immigrants are stealing jobs from them.
"It may seem surprising, but study after study has shown that immigration actually improves wages to U.S.-born workers and provides more job opportunities for U.S.-born workers," he told ABC News. "The fact is that immigrants often push U.S.-born workers up in the labor market rather than out of it."
Despite their status, unauthorized immigrants still contribute "so much in taxes" because they, just like U.S. citizens, have to pay property taxes for their homes or apartments they own or rent, and they also often pay sales taxes for purchases they make, Wiehe explained.
"Researchers have also found that the vast majority of unauthorized immigrants also pay income tax using something called an I-10 income tax return form," she said.
Wiehe added that it is "critical to remember that we are talking about real people here — mothers, fathers and families who are contributing to our society through their work and the taxes they're paying."
ABC News' Riley Beggin contributed to this report.