第8章完全競争
Key Concepts and Summary重要概念とまとめ
As a perfectly competitive firm produces a greater quantity of output, its total revenue steadily increases at a constant rate determined by the given market price. Profits will be highest (or losses will be smallest) at the quantity of output where total revenues exceed total costs by the greatest amount (or where total revenues fall short of total costs by the smallest amount). Alternatively, profits will be highest where marginal revenue, which is price for a perfectly competitive firm, is equal to marginal cost. If the market price faced by a perfectly competitive firm is above average cost at the profit-maximizing quantity of output, then the firm is making profits. If the market price is below average cost at the profit-maximizing quantity of output, then the firm is making losses.
英語のヒント
完全競争企業が生産量を増やすと、総収入は所与の市場価格で決まる一定の率で着実に増える。総収入が総費用を最大の額で上回る数量で利潤が最大となり、または総収入の不足額が最小の数量で損失が最小となる。別の見方では、完全競争企業にとって価格と等しい限界収入が、限界費用と等しいところで利潤は最大になる。その数量で市場価格が平均費用より高ければ利潤を得て、低ければ損失を被る。
If the market price is equal to average cost at the profit-maximizing level of output, then the firm is making zero profits. We call the point where the marginal cost curve crosses the average cost curve, at the minimum of the average cost curve, the “zero profit point.” If the market price that a perfectly competitive firm faces is below average variable cost at the profit-maximizing quantity of output, then the firm should shut down operations immediately. If the market price that a perfectly competitive firm faces is above average variable cost, but below average cost, then the firm should continue producing in the short run, but exit in the long run. We call the point where the marginal cost curve crosses the average variable cost curve the shutdown point.
英語のヒント
利潤最大化生産量で市場価格が平均費用と等しければ、利潤はゼロである。限界費用曲線が平均費用曲線の最小点で交わる点を「ゼロ利潤点」と呼ぶ。完全競争企業の市場価格が利潤最大化生産量での平均可変費用を下回るなら、すぐ操業を止めるべきである。平均可変費用より高く平均費用より低いなら、短期は続け、長期には退出すべきである。限界費用曲線と平均可変費用曲線の交点を操業停止点と呼ぶ。
Self-Check Questions理解度確認問題
Exercises 8–11練習問題 8–11
Exercise 8問題 8
Look at Table 8.12. What would happen to the firm’s profits if the market price increases to $6 per pack of raspberries?
英語のヒント
表8.12を見よう。市場価格がラズベリー1パック6ドルに上がると、企業の利潤はどうなるか。
Quantity 数量 |
Total Cost 総費用 |
Fixed Cost 固定費用 |
Variable Cost 変動費用 |
Total Revenue 総収入 |
Profit 利潤 |
|---|---|---|---|---|---|
0 |
$62 |
$62 |
- |
$0 |
−$62 |
10 |
$90 |
$62 |
$28 |
$60 |
−$30 |
20 |
$110 |
$62 |
$48 |
$120 |
$10 |
30 |
$126 |
$62 |
$64 |
$180 |
$54 |
40 |
$144 |
$62 |
$82 |
$240 |
$96 |
50 |
$166 |
$62 |
$104 |
$300 |
$134 |
60 |
$192 |
$62 |
$130 |
$360 |
$168 |
70 |
$224 |
$62 |
$162 |
$420 |
$196 |
80 |
$264 |
$62 |
$202 |
$480 |
$216 |
90 |
$324 |
$62 |
$262 |
$540 |
$216 |
100 |
$404 |
$62 |
$342 |
$600 |
$196 |
Solution解き方
Holding total cost constant, profits at every output level would increase.
英語のヒント
総費用が一定なら、すべての生産量で利潤が増える。
Exercise 9問題 9
Suppose that the market price increases to $6, as Table 8.13 shows. What would happen to the profit-maximizing output level?
英語のヒント
表8.13のように市場価格が6ドルへ上がるとする。利潤最大化の生産量はどうなるか。
Quantity 数量 |
Total Cost 総費用 |
Fixed Cost 固定費用 |
Variable Cost 変動費用 |
Marginal Cost 限界費用 |
Total Revenue 総収入 |
Marginal Revenue 限界収入 |
|---|---|---|---|---|---|---|
0 |
$62 |
$62 |
- |
- |
$0 |
- |
10 |
$90 |
$62 |
$28 |
$2.80 |
$60 |
$6.00 |
20 |
$110 |
$62 |
$48 |
$2.00 |
$120 |
$6.00 |
30 |
$126 |
$62 |
$64 |
$1.60 |
$180 |
$6.00 |
40 |
$144 |
$62 |
$82 |
$1.80 |
$240 |
$6.00 |
50 |
$166 |
$62 |
$104 |
$2.20 |
$300 |
$6.00 |
60 |
$192 |
$62 |
$130 |
$2.60 |
$360 |
$6.00 |
70 |
$224 |
$62 |
$162 |
$3.20 |
$420 |
$6.00 |
80 |
$264 |
$62 |
$202 |
$4.00 |
$480 |
$6.00 |
90 |
$324 |
$62 |
$262 |
$6.00 |
$540 |
$6.00 |
100 |
$404 |
$62 |
$342 |
$8.00 |
$600 |
$6.00 |
Solution解き方
When the market price increases, marginal revenue increases. The firm would then increase production up to the point where the new price equals marginal cost, at a quantity of 90.
英語のヒント
市場価格が上がると限界収入も増える。企業は、新しい価格が限界費用と等しくなる数量90まで生産を増やす。
Exercise 10問題 10
Explain in words why a profit-maximizing firm will not choose to produce at a quantity where marginal cost exceeds marginal revenue.
英語のヒント
利潤最大化企業が、限界費用が限界収入を超える数量で生産しない理由を、言葉で説明しなさい。
Solution解き方
If marginal costs exceeds marginal revenue, then the firm will reduce its profits for every additional unit of output it produces. Profit would be greatest if it reduces output to where MR = MC.
英語のヒント
限界費用が限界収入を超えると、追加1単位を作るたびに利潤が減る。MR＝MCまで生産量を減らせば、利潤は最大になる。
Exercise 11問題 11
A firm’s marginal cost curve above the average variable cost curve is equal to the firm’s individual supply curve. This means that every time a firm receives a price from the market it will be willing to supply the amount of output where the price equals marginal cost. What happens to the firm’s individual supply curve if marginal costs increase?
英語のヒント
平均可変費用曲線より上の限界費用曲線は、企業の個別供給曲線と等しい。これは、市場から価格を受け取るたびに、価格が限界費用と等しい生産量を供給しようとすることを意味する。限界費用が増えると、個別供給曲線はどうなるか。
Solution解き方
The firm will be willing to supply fewer units at every price level. In other words, the firm’s individual supply curve decreases and shifts to the left.
英語のヒント
どの価格水準でも供給しようとする数量が減る。つまり個別供給曲線は減少して左へ移る。