Supply side shocks
The level of national income can change in the short term if there is a supply-side shock. Many factors can bring about a sudden changes in supply, including changes in the following:
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Wage levels, which affect firms’ unit labour costs.
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Other costs of production, such as commodity prices, or which changes in oil prices are significant.
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Indirect taxes, such as VAT.
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Subsidies.
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Productivity of factors, especially labour.
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Changes in the use of technology and production methods.
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Direct taxes, such as income tax, via an incentive or disincentive effect.
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Length of the working week.
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Labour migration.
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The effect of cost shocks
A cost shock will affect the aggregate supply curve in the short run, and the AS curve will shifts upwards and to the left.

Taking the example of a wage shock, the increase in wages will lead to a rise in business costs, which will shift the AS curve shift upwards, causing the price level will rise from P to P1.
This will cause a contraction of AD, and equilibrium will fall to Y1, resulting in a fall in real output and a probable loss of jobs.Therefore, cost shocks can result in serious economic difficulties for the affected country. Increases in oil prices are always a concern because of the general inflationary effects they can create.









