4. Economic considerations. Ultimately, economics determines whether a mining method should be chosen, because economic factors affect output, investment, cash flow, payback period, and profit. a. Reserves (tonnage and grade) b. Production rate (output per unit time) c. Mine life (total operating period for development and exploitation) d. Productivity (tons or tonnes/employee hour) e. Comparative mining costs of suitable methods f. Comparative capital costs of suitable methods 5. Technological factors. The best match between the natural conditions and the mining method is sought. Specific methods may be excluded because of their adverse effects on subsequent operations (e.g., processing, smelting, environmental problems, etc.). a. Recovery (proportion of the ore that is extracted) b. Dilution (amount of waste that must be produced with the ore) c. Flexibility of the method to changing conditions d. Selectivity of the method (ability to extract ore and leave waste) e. Concentration or dispersion of workings f. Ability to mechanize and automate g. Capital and labor intensities