Which segues neatly into the next question.
Why doesn't the US government have a better (indeed almost perfect) econometric model?
The US government is an obsessive/compulsive collector of data, and has been for at least 50 years. With the provisions of the Patriot Act and several anti money laundering acts, they have the capability of tracking any significant money flow [Ask Governor Spitzer just how detailed]. The IRS has a detailed long-term database. The CIA, NSA, etc. exist to collect covert and confidential data, governmental and private. It employs many of the best and brightest economists, statisticians, actuaries, mathematicians, operations researchers, quants, etc. It operates the world's fastest and most powerful computers, and has some of the world's best programmers. It continuously monitors the internet.
So what exactly is the problem?
Why does economics continue to be taught from the viewpoint of "the Wealth of Nations" first published in 1776, possibly augmented by a British banker's arguments against the Napoleon's "Continental System" published in 1817, that was largely a compilation of his earlier screeds and propaganda efforts for the British government?
One example of the type of critical analysis that could/should be being done is detailed "input/output analysis." This will help identify the critical economic sectors, especially as the underlying model is refined and data accumulated over time.
------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).