China says that it's curtailed supplies because extracting rare elements from ore is very damaging to the environment.
But taxing oil companies could discourage exploration and investment, curtailing supply and driving oil prices up.
The drop occurred despite the looming threat of hurricanes and tropical storms that could curtail supply.
Energy stocks rose on reports that the members of the Organization of the Petroleum Exporting Countries might agree to curtail supply in efforts to reverse the recent slide in oil prices.
In January, the E.P.A. proposed more specific limits on domestic production for the coolant, in the hope that curtailing supply would force "more recovery and reuse of HCFC-22 in large systems, as well as encourage transition to HCFC-22 alternatives".
Oil companies and dealers responded to the Administration's insult by curtailing supply, limiting customers to half a tank's purchase, shutting down early and closing on Sundays.
Regulators ordered utilities to curtail supplies to big commercial users that have agreed to cut consumption in times of shortage.
For 70 years it has bought and hoarded competitors' stones to curtail supplies in the $7 billion uncut-diamond market.
OPEC does not fix global oil prices but its decisions to increase or curtail supplies have a direct impact on oil markets.
Analysts say the increase is being driven by investor expectations of an economic recovery, the recent fall of the dollar against other currencies and, to a lesser extent, the success of oil-exporting countries in curtailing supplies.
To reduce the strain on California's electric grid, regulators ordered utilities to curtail supplies to big commercial users that have agreed to cut their electric consumption in times of shortage.
