An excellent question. The "Field of Dreams" issue arises here. In the presence of sharp learning by doing effects, the government commitment can solve the time consistency issue as the government promises a big push. (1/N) https://twitter.com/mjamurphy/status/1331658793126649865

Consider a possible Gary Becker problem set. There are J cities that face a flooding challenge. The cities can be ordered from the highest willingness to pay city to the lowest regarding offsetting flood risk. The current price of the flood offset technology is $F. (2/N)

The cost of supply the flood mitigation technology is a decreasing function of cumulative experience. Should the Federal Government tax each resident a lump sum amount and pre-commit to purchase X units of this technology?

A tradeoff emerges. If the Feds purchase the X units then the cost of supplying the resilience infrastructure to the J cities decline (learning by doing) and more cities at the margin adopt the technology. The loser here are the lowest valuation cities who must pay the tax.

In this homework, each city's consumer surplus with and without the government policy can be calculated. Aggregating these and taking account the marginal cost of funds would allow for a proper welfare analysis of the Green Big Push on Seawalls.