Millions of Bay Area residents have a stake in the behemoth immigration bill that has now reached a boiling point in Congress.

One of every three residents of our cosmopolitan region was born in another country, drawn here by Silicon Valley dreams or persecution or economic hardship in their native lands.

Half a million Bay Area residents are living here illegally. Others are immigrants who long ago became American citizens -- but still have relatives hoping to join them.

When Congress returns this week from a two-week recess, a bipartisan group of eight senators and another group in the House of Representatives is expected to unveil long-debated immigration proposals that, if passed, could mark the most dramatic and comprehensive overhaul of immigration policy in decades.

Ruben Bernal yells for support of the Dream Act during a rally in front of the school library at San Jose State University on Nov. 30, 2010.
Ruben Bernal yells for support of the Dream Act during a rally in front of the school library at San Jose State University on Nov. 30, 2010. (Gary Reyes/Staff file)

Here's a glimpse of eight groups of people who have the most at stake:

IMMIGRANT FAMILY MEMBERS

How many: Two-thirds of all new immigrants last year -- about 681,000 people -- obtained their green cards because of family connections: They were the spouses, parents, children or siblings of U.S. citizens or legal permanent residents.

Where they're from: Everywhere in the world, led by Mexico, the Philippines and China.

What could change: Siblings and the adult sons and daughters of U.S. citizens already have the longest immigration waits, but congressional Republicans are talking about entirely cutting off the immigration of brothers, sisters and adult married children to admit more immigrants who show they have skills that would help boost the economy.

Political outlook: Most Democrats and immigrant advocacy groups want to keep family reunification the priority in the immigration system. But leading Republicans say the current system results in "chain migration." They would like to reduce visas for family members in favor of a system based more on work skills and economic demand, following the immigration models of Canada, Australia and other rich countries.

HIGH-TECH WORKERS

How many: 85,000 skilled foreign workers are now welcomed annually to the United States on temporary H-1B visas for "specialty occupations" such as computer programming. Silicon Valley recruits the biggest concentration, and thousands more come through other employer-sponsored visas such as the L-1 for international company transfers.

Where they're from: India leads the pack, followed by Canada, Mexico and China.

What could change: One proposal would more than triple the number of H-1B visas to as many as 300,000, though senators have reportedly rejected that number for a smaller expansion. A rival plan could restrict and reform the three-year visas and curb their use by some India-based companies that now dominate the program. Still other proposals would shift the emphasis from temporary to permanent visas, freeing foreign workers from being handcuffed to the employers that hired them. One proposed permanent residency visa would go to as many as 75,000 startup entrepreneurs who raise at least $100,000 and whose companies employ local workers.

Who else could be affected: Opponents of an expansion argue that a glut of foreign tech workers -- especially temporary workers beholden to their employers -- drives down wages and displaces older American engineers.

Political outlook: Temporary work visas are one of the most hotly contested provisions of proposed immigration legislation but have influential backing from the tech lobby. Green cards for startup entrepreneurs and science graduates have broader support but affect a smaller group of would-be immigrants.

DREAM ACT STUDENTS

How many: More than a million children and young adults were brought to the United States illegally before they were 16. About 65,000 live in the Bay Area.

Where they're from: The majority are from Latin America. About 10 percent nationwide and nearly half in the University of California system are from Asia.

What could change: Since September, the Obama administration has granted work permits and temporary protection from deportation to 200,000 young illegal immigrants who applied for relief. But only Congress can grant them permanent residency and citizenship.

Political outlook: Known as "dreamers" because their fate has long been attached to the never-passed Dream Act, first introduced in 2001, these young immigrants have won the most sympathy in the immigration reform debate. Most Americans and lawmakers now favor granting them a fast track to citizenship, but their parents will probably face a more arduous path.

UNDOCUMENTED ADULT IMMIGRANTS

How many: The U.S. has roughly 10 million undocumented immigrants who arrived as adults by illegally crossing the border or overstaying a temporary visa.

Where they're from: About 58 percent are from Mexico, with large numbers also from Central America and Asia.

What could change: The leading Senate proposal would offer them a 13-year path to citizenship if they pay a penalty and meet other requirements. For the first 10 years, they'd be on a probationary legal status, in which they could work legally but not have access to government benefits. Lawmakers are negotiating enforcement provisions, such as electronic worker verification, aimed at blocking future flows of illegal immigration.

Who else would be affected: Bringing millions of people from the shadows into the legal workforce would have broad effects on the economy and society. Advocates say increasing their opportunities helps the economy and encourages participation in civic life. But opponents warn of job competition in low-wage occupations between newly legalized and native-born Americans who don't have high school or college degrees.

Political outlook: A growing consensus has emerged since the historic Latino and Asian-American turnout for Democrats in the November election, as more Republican lawmakers, including tea party members, have endorsed a pathway to citizenship or some form of legalization.

FARM AND GUEST WORKERS

How many: About 55,000 farmworkers entered the United States in 2011 on seasonal visas that last up to 10 months, but many more migrants who work in the fields are living here illegally -- including most of California's 800,000 farmworkers. Companies also hired another 50,000 guest workers in nonagricultural jobs, which ranged from cleaning hotels to operating carnival rides.

Where they're from: Mostly Mexico and Central America.

What could change: A new "blue card" could grant a speedy pathway to legal residency for farmworkers already here, but legislation could also bring big changes to the nation's underutilized guest-worker programs for farmworkers, factory workers and other manual laborers. Senators are proposing a new W visa that, unlike current guest work visas, would allow nonagricultural workers recruited from abroad to switch jobs and eventually petition to stay in the country permanently.

Who else is affected: Farmers and domestic food production and prices depend on the availability of immigrant labor, but legalizing farmworkers already here could also push them to find better-paying jobs in the cities, increasing job competition among other low-skill workers. U.S. construction workers are among those most concerned about competing with immigrants, though a new guest visa proposal would limit its usage in the construction industry.

Political outlook: Labor unions, business groups and top lawmakers came to a compromise just before Easter after a months-long debate over how many nonagricultural guest workers to allow, what should be their minimum wage and how to prevent worker exploitation. But similar talks on farmworkers collapsed, raising uncertainty about whether the reform bill will include agriculture.

THOSE WAITING FOR A GREEN CARD

How many: About 4.5 million people are waiting for a green card.

Where they're from: Mostly Mexico, the Philippines, India, Vietnam, China and the Dominican Republic.

What could change: The wait for family visas is several decades long from countries with the highest demand, such as Mexico and the Philippines. Congress could reduce waiting times for some and lengthen it for others by lifting the caps that limit how many immigrants can come from any one country.

Political outlook: Some support exists in Congress for lifting the per-country caps, especially for employment-based visas that mostly affect prospective immigrants from populous countries such as India and China.

FOREIGN GRADUATE STUDENTS

How many: Tens of thousands of foreign graduate students studying science or technology.

What could change: For the first time, an unlimited number of highly educated foreigners each year could get a fast track to permanent U.S. residency if they earn a master's or doctoral degree from a U.S. university in the so-called STEM fields: science, technology, engineering or math.

Who else this will affect: Giving the best-educated foreigners an easier path to stay in the country permanently could lessen their dependence on temporary work visas. But opponents fear the green card incentive will flood U.S. universities with elite foreigners, crowding out American students who pay lower tuition.

Political outlook: There's broad support in both parties for the STEM green card, designed to retain foreign scientists and engineers who would otherwise go back home or have to navigate for years through America's temporary-visa programs

THE LOTTERY WINNERS

How many: Up to 55,000 people from around the world each year are randomly awarded a "diversity visa" through a lottery.

Where they're from: Countries with low rates of emigration to the United States. In recent years, nearly half the lottery winners came from Africa.

What could change: Republicans propose to eliminate all 55,000 visas to make more room for immigrants with U.S. graduate degrees or needed skills.

Political outlook: The lottery's defenders say it's still the only route for aspiring Americans who don't have existing family or work connections in the United States. But in the push for more skills-based immigration, the lottery could very likely be on the chopping block.