WASHINGTON – The Senate last week passed legislation that Sen. Edward Kennedy, D-Mass., hailed as “the most far-reaching immigration reform in our history.” You might think that the first question anyone would ask is how much it would actually increase or decrease legal immigration. But no.

After the Senate approved the bill by 62 to 36, you could not find the answer in the news columns of The Washington Post, New York Times or Wall Street Journal. Yet, the estimates do exist and are fairly startling. By rough projections, the Senate bill would double the legal immigration that would occur during the next two decades from about 20 million (under present law) to about 40 million.

One job of journalism is to inform the public what our political leaders are doing. In this case, we failed. The Senate bill’s sponsors didn’t publicize its full impact on legal immigration, and we didn’t fill the void. It’s safe to say that few Americans know what the bill would do because no one has told them. Indeed, I suspect that many senators who voted for the legislation don’t have a clue as to the potential overall increase in immigration.

It is interesting to contrast these immigration projections with a recent opinion survey done by the Pew Research Center. The poll asked whether the present level of legal immigration should be changed. The response: 40 percent favored a decrease, 37 would hold it steady and 17 percent wanted an increase. There seems to be scant support for a doubling. If the large immigration projections had been in the news, would the Senate have done what it did? Possibly, though I doubt it.

But if it had, senators would have had to defend what they were doing as sound public policy. That’s the real point. They would have had to debate whether such high levels of immigration are good or bad for the country. What arguments would they have used?

No one can contend that the United States needs expanded immigration to prevent the population from shrinking. Our population is aging but not shrinking. With present immigration policies, the Census Bureau projects a U.S. population of 420 million in 2050, up from 296 million in 2005.

Another dubious argument is that much higher immigration would dramatically improve economic growth. From 2007 to 2016, the Senate bill might increase the economy’s growth rate by a tiny 0.1 percentage point annually, estimates the Congressional Budget Office.

The doubling of legal immigration under the Senate bill that I cited at the outset comes from a previously unreported estimate made by White House economists. Because the president praised the Senate bill, the administration implicitly favors a big immigration expansion. The White House estimate could be low. Robert Rector of the conservative Heritage Foundation has a higher figure. The CBO has a projection that the White House describes as close to its own. But all the forecasts envision huge increases.

Our immigration laws involve a bewildering array of categories by which people can get a “green card” – the right to stay permanently. The Senate bill dramatically expands many of these categories and creates a large new one: “guest workers.” The term is really a misnomer, because most “guest workers” would receive an automatic right to apply for a green card and remain. The Senate bill authorizes 200,000 “guest workers” annually, plus their spouses and minor children.

One obvious question is why most of the news media missed the larger immigration story. On May 15, Republican Sen. Jeff Sessions of Alabama held a news conference with Heritage’s Rector to announce their immigration projections and the estimated impact on the federal budget. Most national media didn’t report the news conference. The next day, CBO released its budget and immigration estimates. These, too, were largely unreported.

Rector’s explanation is that the news media’s “liberal” bias creates a pro-immigration slant. I think it’s more complicated. Stories generally mirror the prevailing political debate, which has concentrated on “amnesty” for existing illegal immigrants and the “guest worker” program. Increases in other immigration categories were largely ignored.

Reporters also cover legislative stories as sports contests – who’s winning, who’s losing – rather than delve into dreary matters of substance.

But note the irony: the White House’s projected increases of legal immigration (20 million) are about twice the level of existing illegal immigrants (estimated between 10 million and 12 million). Yet, coverage overlooks the former. Here, I think, Rector has a point. Whether or not the bias is “liberal,” group-think is a powerful force in journalism. Immigration is considered noble. People who critically examine its value or worry about its social effects are considered small-minded, stupid or bigoted. The result is selective journalism that reflects poorly on our craft and detracts from democratic dialogue.