On the 2016 presidential campaign, immigration is the dominant domestic issue. Some candidates want to legalize the 12 million plus unlawful immigrants, others’ goal is to increase the level of about one million legal immigrants the United States accepts annually, and another group seeks to expand the number of guest worker visas issued. Several contenders want to do all three—grant amnesty, increase legal immigration, and give more guest visas to overseas workers.

Lost in the candidates’ competing positions is a historical look on where the U.S. has been on immigration, and where it might be going. Specifically omitted from the presidential hopefuls’ rhetoric, and purposely so, is what effect continuously high immigration has and continue to have on American workers. A wealth of statistics from non-partisan sources indicate that sustained high immigration has hurt American workers across all demographic subsections.

Inexplicably, when it comes to federal immigration policy, economic conditions really don’t play a role. Whether the economy is adding jobs or in a recession, immigration continues on autopilot at the approximately one million annual level. And the demand for guest workers, currently at about 750,000 yearly, continues. From California’s Silicon Valley led by IT industries executives like Mark Zuckerberg to Vermont’s dairy farms, the cry is the same: We can’t find American workers.

The sharp decline to 62.6 percent in the labor-force participation rate—the share of people holding jobs or seeking them—shows that employable people have dropped out of the workforce. White House officials offer many excuses for the phenomena—automation, baby boomers hitting retirement age, or voluntary retirement.

But there’s no way to positively interpret the labor-force participation drop. Buried in its footnotes, the Bureau of Labor Statistics reveals the true reason for the decline. The BLS provides data on the “native-born” workers. Since the Great Recession, the U.S. has added 2.3 million foreign-born workers, but only 727,000 Americans, a verifiable fact. The surge in overseas workers also explains the stagnant wages Americans have endured for decades. Many of the foreign-born jobs go to illegal immigrants who, although they work hard, have no bargaining power. After all, without work authorization documents, the illegal immigrants are simply happy to be employed. Thus, native-born workers performing the same jobs as illegal immigrants endure depressed earnings.  According to a Pew Hispanic Center report, 8 million illegal immigrants held U.S. jobs in 2010, including seven million in the non-farm sector. Only four percent worked in agriculture, forestry or fishing.

The eight million total may soon increase. The Center for Migration Studies, a pro-immigration organization, estimates that 2.5 million illegal immigrants have settled in the U.S. since President Obama’s inauguration, and arrived by crossing the border or overstaying their visas.

Even though no less an authority than Labor Secretary Thomas Perez acknowledges that the labor market has “a significant amount of slack,” he endorses President Obama’s executive action amnesty that would add more workers at a time when the economy cannot absorb them.

To the surprised of many, illegal immigration was even higher under President George W. Bush, an average of 500,000-600,000 for each of his eight years in office. The combined Bush-Obama failure to enforce immigration laws proves that, no matter the economy’s depressed condition, legal immigrants and illegal aliens continue to arrive unchecked and with slight chance of deportation. As a result, American workers are displaced in increasingly large numbers.

Yet despite minimal awareness among the general public about the link between high immigration and American job loss, the subject is taboo on the campaign trail. With 15 months to go before November 2016, time remains for candidates to enlighten the electorate. Whether they will remains to be seen.

Joe Guzzardi is a Californians for Population Stabilization Senior Writing Fellow whose columns have been syndicated since 1987. Contact him at joeguzzardi@capsweb.org