A table answer earns full marks when it says what the numbers show and why they behave that way. Repeating the calculation shows only the first half.
This lesson is part of cost and productivity from a supplied table. The general writing pattern is in writing cause, mechanism and effect explanations.
What does an explanation contain?
Use three parts in order.
- Claim: what happens, in words.
- Evidence: one or two figures from the table.
- Reason: the economic idea that makes it happen.
The claim and evidence revision desk lets you practise splitting your own sentences into these parts.
Worked example: a fictional kitchen with one oven
| Workers | Total output (trays) | Marginal product |
|---|---|---|
| 1 | 20 | 20 |
| 2 | 48 | 28 |
| 3 | 70 | 22 |
| 4 | 84 | 14 |
| 5 | 90 | 6 |
The question: “Explain the change in marginal product from the second to the fifth worker.”
Marginal products are found by subtracting: 48 − 20 = 28, 70 − 48 = 22, 84 − 70 = 14 and 90 − 84 = 6.
Repeating versus explaining
| Answer | Content |
|---|---|
| Repeating | “MP is 28, then 22, then 14, then 6.” |
| Explaining | “Marginal product falls from 28 to 6 after the second worker. The kitchen has only one oven, which is fixed in the short run. More workers must share it, so each extra worker adds less. This is diminishing returns.” |
The first answer only re-reads the table. The second names the claim (falls), the evidence (28 to 6), and the reason (a fixed oven shared by more workers).
Notice the phrase “in the short run”. It signals which assumption makes the reason valid, and it links back to the short run and long run lesson.
The mistake that costs marks
The common slip is ending at the number. “The MP of the fifth worker is 6” is correct, but answers neither “explain” nor “why”.
A second slip is giving a reason the table cannot support, such as “the workers became lazy”. Use the structure that the table shows: fixed input, more variable input.
Check yourself
A fictional fish-drying shed has one drying rack. Total output with 1, 2, 3 and 4 workers is 15, 36, 54 and 62 kg. Explain the change in marginal product from the second to the fourth worker.
Answer
MP of the second = 36 − 15 = 21. MP of the third = 54 − 36 = 18. MP of the fourth = 62 − 54 = 8.
A full answer: “Marginal product falls from 21 kg to 8 kg as workers are added. The shed has one drying rack, which is fixed in the short run. Each extra worker shares the same rack, so adds less output than the one before. This is diminishing returns.”
What to study next
Test all four skills in the integrated practice. To review how to recover blanks, revisit recovering a missing cost value.
If you want a teacher to read your written reasons with you, see online one-to-one Economics tuition.