『Abstract
　We study the cost of coal-fired electricity in the United States between 1882 and 2006 by decomposing it in terms of the price of coal, transportation cost, energy density, thermal efficiency, plant construction cost, interest rate, capacity factor, and operations and maintenance cost. The dominant determinants of cost have been the price of coal and plant construction cost. The price of coal appears to fluctuate more or less randomly while the construction cost follows long-term trends, decreasing from 1902 to 1970, increasing from 1970 to 1990, and leveling off since then. Our analysis emphasizes the importance of using long time series and comparing electricity generation technologies using decomposed total costs, rather than costs of single components like capital. By taking this approach we find that the history of coal-fired electricity suggests there is a fluctuating floor to its future costs, which is determined by coal prices. Even if construction costs resumed a decreasing trend, the cost of coal-based electricity would drop for a while but eventually be determined by the price of coal, which fluctuates while showing no long-term trend.

Keywords: Coal; Electricity; Historical cost』

1. Introduction
2. Historical data
　2.1. Data sources
　2.2. Decomposition formula
　2.3. Fuel cost
　　2.3.1. Coal price
　　2.3.2. Transportation costs
　　2.3.3. Coal energy density
　　2.3.4. Thermal efficiency
　　2.3.5. Fuel cost
　2.4. Operation and maintenance cost
　2.5. Capital cost
　　2.5.1. Specific construction cost
　　2.5.2. Capacity factor
　　2.5.3. Interest rate
　　2.5.4. Capital cost
　2.6. Total cost
3. Analysis of cost trends
4. Analysis of cost variation
5. Future implications
　5.1. Commodities versus pure technologies
　5.2. Modeling a commodity
　5.3. modeling a technology
　5.4. Application to coal-fired electricity
6. Conclusions
Acknowledgments
Appendix A. Change decomposition
References