imiyakawa said:
BUT, I think there might actually be a shift in the supply curve as well as the demand curve if you consider what you said: the law of diminishing returns. As the consumer subsidy increases, demand increases, and at some point the cost/unit of production increases (law of diminishing returns). THIS WOULD CAUSE A SHIFT IN THE SUPPLY CURVE, as producers are less inclined to supply. So there would be two competing elements. Of course, consumer demand (shift in D-curve) would outweight increased costs per unit (shift in S-curve) by a huge margin, but the process is there.
As CRGreathouse indicated, you are confusing a movement along the supply curve with a shift of the supply curve, and you are half-correct when you say the only thing that causes a movement along the supply curve is a change in price* (in your response to CRG, quoting wikipedia). More importantly, what you have postulated is, at best, a second-order effect, sort of like "Reaganite" supply-side economics (aggregate supply "will eventually" shift to the right in response to lower taxes). But the OP is about the first-order effects; it's a simple microeconomic question that does not require the macroeconomic analysis that you have attempted.
To focus on the microeconomics, the analysis is the same whether it's the demand curve or the supply curve "doing the shifting." A subsidy is like a reverse tax (negative tax), so subsidy analysis is qualitatively identical to tax analysis. Starting with a positive tax,
this graph indicates that there is a pre-tax equilibrium with one price, and a post-tax equilibrium with two prices -- the difference between the two prices accrues to the taxing authority ("the difference belongs to the government"). You can represent the post-tax equilibrium either by shifting the demand curve along the supply curve down, to P
p, or by shifting the supply curve along the demand curve up, to P
c, and the results of the analysis will be the same regardless of which graphical representation is used. In essence that's what CRGreathouse was pointing to by indicating that the [first-order] result of a subsidy (or, for that matter, a tax) is a shift in one of the curves which corresponds to a movement along the other curve.
For a negative tax (that is, a subsidy), one would shift the demand up (consumer subsidy), or the supply down (producer subsidy), while the other curve does not shift.
ALSO, the question asked the consequences of this subsidy to industry. You should talk about how perhaps, if it was an oligopolistic industry, new players would flood into the industry resulting from increased demand and the market may actually become monopolistic or perfect-competition in its tendencies.
You could then talk about future potential consequences of this if the subsidy was removed, and how the industry would be forced back to equilibrium; i.e. all excess firms will die out.
You could then talk about how, post-subsidy, the amount of firms left over actually EXCEEDS the amount of firms in the initial market, EVEN IF THE POST-SUBSIDY DEMAND IS THE SAME SIZE AS THE PRE-SUBSIDY DEMAND. This is because these extra firms have overcome all natural barries to entry that was stopping perfect competition in the original market!
Here you are confusing short-run with the long run. This is a short-run analysis. The (short-run) supply curve incorporates the productive capacity of all the firms in the market, or the industry. The picture that the OP provided indicates that the firms existing in the industry are able to meet the increased demand, although at a higher price. The higher price is the "cost" of bringing in higher-cost firms (or facilities, plants, machines) that were not being used before the demand shift. But that does not mean there is new firms entering; what's being used is existing "excess" capacity that can start producing at short notice.
I will not go into long-run analysis here, only point out that more firms entering the market in response to a demand increase is a non-sequitur; there is simply not enough information to decide whether there is going to be entry or exit into this industry, with or without the subsidy. For example, we don't know anything about firms' profits, or their fixed or average costs.
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*That's because the supply curve is the graphical representation of the marginal cost of supplying a given quantity -- so, when the price rises along a supply curve, more productive capacity is brought in-line at a higher cost because consumers are demanding it. On a supply curve, "price" is really the measure of (and remuneration for) the supply cost. Just like on a demand curve "price" is the measure of (and "opportunity cost" of) consumer utility.