Answer
YES, the increase in the average price of houses due to the construction of the barrier should be considered in the economic justification.
Solution
a
Expected Annual Loss Without Barrier: Calculate the expected annual loss due to avalanches without the barrier
The expected annual loss is the product of the probability of the event and the total loss if the event occurs. Using the given data, the expected annual loss is $\frac{1}{1200} \times 200 \times \$180,000 = \$30,000$.
b
Expected Annual Benefit of the Barrier: Calculate the expected annual benefit of the barrier in terms of increased house prices
The expected annual benefit is the total increase in house prices due to the barrier. The increase for each house is $1,500, so for 200 houses, the total increase is $1,500 \times 200 = \$300,000. Since the houses and the barrier have an infinite lifespan, this is a perpetual benefit. The present value of this perpetual benefit is $\frac{\$300,000}{i}$, where $i$ is the social discount rate.
c
Economic Justification: Compare the cost of the barrier to the sum of the expected annual loss without the barrier and the present value of the increased house prices
The cost of the barrier is \$300,000. The economic justification requires that the cost of the barrier be less than or equal to the sum of the expected annual loss without the barrier and the present value of the increased house prices. Since the expected annual loss is \$30,000 and the present value of the increased house prices is $\frac{\$300,000}{i}$, the barrier is justified if $\$300,000 \leq \$30,000 + \frac{\$300,000}{i}$.
Key Concept
Economic Justification of Investment
Explanation
The construction of the barrier is economically justified if the cost is less than or equal to the sum of the expected annual loss without the barrier and the present value of the increased house prices due to the barrier.