The problem of illegal immigration, as everyone knows, is bad and getting worse. Ask anyone, they'll tell you -- the federal government has abdicated its responsibility to secure the borders, and as a result more and more illegal immigrants cross the border every year. As everyone knows.

There's only one problem with this -- it's not true anymore.

However, these statements lose nothing of their "truthiness." As Stephen Colbert defined this term, this means that it doesn't matter if it is true or not, because it sounds so true that everyone believes it anyway, because they want to believe it's true. [Official Colbert definition (there are actually many Colbert quotes on the subject to choose from): "Truthiness is 'What I say is right, and [nothing] anyone else says could possibly be true.' "]

Of course (snarkiness aside), I'm referring to the new report out from Pew which shows that illegal immigration is actually way down. From the Washington Post article which broke the news:

A deep recession and tougher border enforcement have led to a sharp decline in the number of immigrants entering the United States illegally in the past five years, contributing to the first significant reversal in the growth of their numbers in two decades, according to a new report by the Pew Hispanic Center.

The number of illegal immigrants entering the United States plunged by almost two-thirds between 2005 and 2009, a dramatic shift after years of growth in the population, according to the report.

In the first half of the decade, an average of 850,000 people a year entered the United States without authorization, according to the report, released Wednesday. As the economy plunged into recession between 2007 and 2009, that number fell to 300,000.

The drop has contributed to an 8 percent decrease in the estimated number of illegal immigrants living in the United States, from a peak of 12 million in 2007 to 11.1 million in 2009, the report said.

So, of course, we can all expect the politicians arguing about the issue to revamp their rhetoric and start admitting the true situation, right? Well, in a perfect world, the answer would be yes, but this is far from a perfect world.

Even if it were so, it would just tee up the next argument -- why illegal immigration is down. And that's a dicier prospect, at best, because it gets into questions of causality, which are hard if not impossible to prove one way or another (proving causality would involve a lot of costly research which likely won't get done for years, if ever).

There are many candidates for possible contributing factors, which are likely working simultaneously to differing degrees. The amount of guest worker visas allowed by the U.S. is up, meaning more transitory labor can come here legally. Border enforcement is up, as are deportations. But the elephant in this particular room is most likely the economy itself. There are less jobs available, and therefore the "draw" for illegal immigrants is way down. Some may even be "reverse immigrating," or going back to their countries of origin because they can't find any work, meaning there's no point in their staying.

But politics isn't social science, where causality must be rigorously proven. Politics is, to be blunt, whatever you can get away with saying to the voters. Think not B.F. Skinner, but rather P.T. Barnum, in other words. "Event X happened because party Y passed legislation Z" is an expected statement from a politician, on any subject under the sun. Call it "spin" if you will, but a large part of it lies in convincing the American public that you have a right to claim credit because of your policies.

Meaning it will be interesting to see if either the Democrats or the Republicans change their tune in any way on the immigration debate. Not so much in the policies they are calling for, but rather in the way they speak of the issue itself.

Republicans, one assumes, would boast that: "We forced Bush and Obama to tighten up the border and put money into enforcement, and that is why illegal immigration is down." Democrats would likely say: "This happened while Democrats were in charge of Congress, so the public should put their trust in us to solve immigration, because we are already making such great strides in this area."

Both statements would be judged on the scales of truthiness by the public, since neither one would have any shred of proof attached.

But there's a third option, one which is kind of alarming. And that is that politicians from both sides of the aisle will deny the truth, and not shift their rhetoric in any way whatsoever. Republicans and Democrats will push for their respective policy ideas without acknowledging that the problem appears to be getting better. And it's a measure of their political honesty, in a way, because if politicians across the board continue to speak of the problem as "growing" or "not getting better" than it really shows that they both believe that we are now in a period of aberration in the data, because the economy is down. Meaning they are admitting that no matter what has so far been done on the issue is a bigger factor than pure economic reasons. Which is a rather self-defeating statement for any politician with any policy idea (other than: "let's wreck the U.S. economy so badly that nobody will want to come here," which isn't much of a policy suggestion).

There's a reason both parties may choose this route, because eventually the economy will get better. And if illegal immigration increases as a result, then they will avoid finger-pointing and the whole blame game when we get there. Which is, as I said, a measure of political honesty which not many politicians of either stripe may be capable of.

Which leaves the sole hope of the public that the media will adjust their questions and positions to fit the new data. For instance, "But illegal immigration is actually down, what do you have to say about that?" is the type of question they might begin to ask. But this may be asking too much of the media, because not unlike today's politicians, the media are deeply, deeply in love with truthiness, and show no signs of ending this love affair. If this weren't the case, Stephen Colbert never would have coined the term in the first place, and most of you (I'm guessing) wouldn't even have required me to define it.

In any case, it will certainly be interesting to see if (and how) the immigration debate changes as a result of the new Pew data. Of course, we may have to wait awhile, because it doesn't look likely the Senate is going to do anything on it this year, and next year's Congress may decide not to touch it, either. Just call it idle Thursday speculation on my part, I guess.

-- Chris Weigant

Follow Chris on Twitter: @ChrisWeigant