A citation about GDP, a main indicator being measured and predicted by economics, borrowed from Armageddon on another thread (about hyperinflation):
GDP is about as useless and somebody taking out a loan for a million dollar house and calling themselves wealthy.
This is the point that highlights the predictive value of economics. Specifically, economics should not necessarily be viewed as measuring GDP reactively. Rather, economic models are used to pro-actively generate a certain GDP number.
Suppose you see a house that you like to buy and you have an 250k mortgage limit with your bank. You ask the price from the seller and he says that he has an alternative bidder whose bid is 200k. You bid 250k, but now a third bidder arrives and says that he is prepared to pay 300k. You go to the bank and ask to extend your credit limit to 350k. The bank, on whatever terms, agrees, and you win the auction. You buy the house, pay 350k, and those 350k go to the aggregate GDP number.
So, who or what was the deciding factor in setting up the GDP number? Supply/demand laws? No, this was the credit manager in the bank, who made the decision about your credit limit. He did it on the basis of economic models prevalent at the time of the decision. ( This is of course more complex than that - it also involves background checks, credit history, demographics etc. - but these may be safely assumed to be invariables for the purposes of simplicity). Thus, these economic models in fact generated a certain GDP number, rather than simply explained or forecast it. In this sense, the economics have a strong predictive, even preordaining, value.
Now, what are those economic models? These are in fact mostly financial models which consist of formal relations (NPVs, DCFs etc), assumptions and parameters set by the Fed and budget (interest rates, spending etc.). So these are mostly financial models, and this aspect of economics is almost the usual common sense Finance peppered with some formulas to look cleverly.
Now, what those in charge say to their populace is a different story. They have to hold their people positive and motivated, otherwise the order in the society will start crumbling. So they make exaggerated promises. This is the simplest way to keep people forward-looking and hold their morale intact. It is called "exercising persuasion skills" and practiced to this or that extent in any corporation (unless crisis or layoffs are in sight).
Those in charge do not tend to wish to take risks that come with such promises. Nicolas II agreed to assume the entire responsibility for the conduct of the war - and paid dearly. To cope with the issue of the deem consequences of an unfavorable battle outcome, the Roman Emperors deferred to the Deity: the had their priests to read prophecies on the guts of the sacrificed animals. If the prophecy was unfavorable, they would avoid the battle by all means. If the prophecy was favorable, they would charge the enemy. And then if the Romans would lose the battle, the Emperor could always execute the priests for their ineptness - the Deity could never be wrong. The priests would come and go, but the Emperor would go on untainted in the view of his subjects.
Similarly, those in charge now defer to the Deity of economics via the priestly economists. The economists may then be removed for doing a poor job, but the boss would go on (even though up to a certain point these days). Hence this aspect of the economics is more like the old good Astrology.
With regard to the influence of stimulus on the employment, GDP growth, and alike predictions - it is no more scientific then trying to predict whether Manchester United is going to win against Chelsea. Or the Boston team against Atlanta's. How can the jobs be created in the US without a commensurate loss of jobs in China or another relevant country? The Chinese will compete, and the outcome is no more clear than that of a sporting event, because this competition involves human beings whose behavior and persistence is inherently difficult to predict for all their inner complexity. This is the case even if the rules of the sporting game are simple and formal. So this aspect of economics is similar to Sweepstakes - you can bet on the strongest player, but is still exposed to loss on your bet. By contrast, physics deals with dead objects whose behavior is easily formalized, and therefore is easy to predict unambiguously.
This seems to be detached from the peak oil dimension, but in fact it is linked, via the notion that the growth is now a zero-sum competition game.
Finance, Astrology, Sweepstakes.
- do you even read the links you post - first page of your first link clearly states that there has been a lack of consideration of resource constraint in 20th century economic thinking.