Utah Supreme Court
2008 UT 74, 196 P.3d 601
A required exaction must be roughly proportionate to the impact of a development; otherwise, the exaction is an unconstitutional taking in violation of the Fifth Amendment (and the Utah Constitution’s Takings Clause).
In order for an exaction to be constitutional, a local government must make some determination that the required exaction is related both in nature and extent to the impact of the proposed development.
This analysis has two aspects: First, the exaction and impact must be related in nature; and second, they must be related in extent. The analysis first focuses on whether the nature of the exaction and impact are related. This is accomplished by looking at the exaction and the impact in terms of a problem and a solution. The impact–or the burden the community will bear because of the development–is the problem, and the exaction should address the problem. If it does, the nature component has been satisfied.
The second component of rough proportionality analysis is accomplished by measuring the exaction and the impact by the same standard. The most appropriate measure compares the cost of the exaction to the cost of the impact. The impact of the development can be measured as the cost to the municipality to assuage or address the impact; likewise, the exaction cost can be measured as the value of the land to be dedicated, along with any other required expenses. If the cost to the municipality to address the impact and the cost to comply with the exaction are roughly equivalent, the exaction satisfies the analysis.