Jacob's consumption increased by $12,000.
The marginal propensity to consume is defined as the proportion of an increase in income that a consumer consumes instead of saving.
Amount of disposal income in 2019 = $30,000
Amount of consumption in 2019 = $20,000
Increased disposal income = $40,000
Marginal propensity to consume = 0.8
Increase in consumption = $12,000 ($40,000 x 0.8 - $20,000)
Thus, Jacob's consumption increased by $12,000.
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