1. The Malthusian Model and the Great Irish Famine
David Clingingsmith

2. Malthusian model of population
Population expands if food output per person increases and contracts if it decreases.
Better nutrition means lower death rate
Better nutrition means earlier marriage and higher birth rate.
Nb. when food per person is below subsistence, the fall will be rapid.
Diminishing average product of labor implies that as population increases, food output per person will fall.

3. Diagram of Malthusian Model
Left graph: Diminishing average product of labor implies that as population increases wages will fall. Represented by BLUE line
Right graph: Population expands if real wage higher. Represented by RED line.
Real wage
Real wage
Population growth + -
positive
negative
Population
rising A′ A
Pop
WageSubsistence
Population
falling
Population

4. How would a sudden decline in population affect a Malthusian economy?
Left graph: Diminishing average product of labor implies that as population increases wages will fall. Represented by BLUE line
Right graph: Population expands if real wage higher. Represented by RED line.
Real wage
Real wage
Population growth + -
positive
negative A
PopMedium
WageSubsistence
Population
rising B B′
WageHigh A′
Population
falling
PopLow
Population
Wages would rise, then population would increase, and wages would fall,
leading the economy back to the same equilibrium wage and population

5. The Great Irish Famine of 1845-1850
Ireland is a largely agricultural country in 1845.
Poorest third of the population depend on potato almost exclusively.
Fungus phythophtera infestans (potato blight)
Arrives in 1845
Destroys much of potato harvest through 1848.
Famine caused 1 million deaths, or one eighth of the Irish population.
In terms of the Malthusian model, the potato blight causes a reduction in the average product of labor.
During the famine working in potato fields yields many fewer potatoes per person than before.

6. Malthusian model and the potato blight in Ireland
Left graph: Diminishing average product of labor implies that as population increases wages will fall. Represented by BLUE line
Right graph: Population expands/contracts if real wage increases/decreases. Represented by RED line.
Real wage
Real wage
Population growth + -
positive
negative
Population
rising A′ A
WageSubsistence
Population
falling C′ C B B′
WageStarvation
PopBlight
Pop
Population

7. Malthusian Model and Policy
The Malthusian Model predicts a decline in Irish population through starvation due to the potato blight.
What can government do to prevent deaths?
To the extent blight is temporary, import food and feed people until agriculture recovers.
Having it for sale may not be enough—people have no income to use to buy it.
To the extent blight is long-lasting, support emigration.
The Malthusian model tells us that there will be starvation until enough people die to raise average productivity back to subsistence level.
British policy failed to do enough on both of these dimensions (Black ‘47 and Beyond, O’Grada 1999).

8. The Great Famine and Irish Emigration
By 1850 there had been about one million deaths and one million emigrants due to the famine, reducing the population of Ireland from 8 million to 6 million.
The potato blight did not permanently damage Irish agriculture, but the large- scale outmigration sparked continued emigration throughout the 19th century.