The fact that participants were willing to substitute part of a food item for the mere prospect of a relatively small monetary award is interesting, says Reimann.

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"The fact that participants were willing to substitute part of a food item for the mere prospect of a relatively small monetary award is interesting," says Reimann.

Unfortunately, the current low prices for oil, gas, and coal may provide little incentive for research to find even cheaper substitutes for those fuels.

In addition, other factors are putting downward pressure on oil prices: change in the strategic behavior of the Organization of Petroleum Exporting Countries, the projected increase in Iranian exports, the scaling-down of global demand ( ' , especially from emerging markets), the long-term drop in petroleum consumption in the United States, and some displacement of oil by substitutes.

Direct subsidies to research and development have been adopted by some governments but are a poor substitute for a carbon price: they do only part of the job, leaving in place market incentives to over-use fossil fuels and thereby add to the stock of atmospheric greenhouse gases without regard to the collateral ( ' , 附帶的) costs.

The sales of tobacco substitutes have increased considerably.

Direct subsidies to research and development have been adopted by some governments but are a poor substitute for a carbon price: they do only part of the job, leaving in place market incentives to over-use fossil fuels and thereby add to the stock of atmo

When considering the amount of insurance for the mother with dependent children, substitute child care is a need that should be planned for until the children can care for themselves.