From Global nuclear stockpiles, 1945-2006 | thebulletin.org:
More than 128,000 nuclear warheads have been built since 1945, according to our calculations, and all but close to 3 percent were built by the United States (about 55 percent) and the Soviet Union/Russia (about 43 percent). Since the end of the Cold War, the United States and Russia have moved an increasing percentage of their warheads from operational status to various reserve, inactive, or contingency categories, as arms control agreements traditionally have not required the destruction of warheads. For example, the 2002 Strategic Offensive Reductions Treaty (the "Moscow Treaty") contains no verification provisions and ignores nonoperational and nonstrategic warheads altogether. With any number of warheads in indeterminate status, nuclear stockpiles are becoming more opaque and difficult to describe with precision. It's a situation that will only worsen after 2009 if the United States and Russia do not extend the Strategic Arms Reduction Treaty I, which requires biannual reporting on the status of intercontinental ballistic missiles, submarine-launched ballistic missiles (SLBMs), and bombers.
United States. The Pentagon has custody of approximately 10,000 stockpiled warheads, of which about 5,735 are considered active or operational. The remaining are categorized as reserve or inactive. Details from an Energy Department 2004 stockpile plan indicate that some 4,000 warheads will eventually be retired, returned to Energy's custody, and disassembled at the Pantex Plant near Amarillo, Texas, though that task could take many years to accomplish. Refurbishments and upgrades to existing warheads will take priority over disassembly in terms of man-hours for the foreseeable future.
Of the more than 70,000 warheads produced by the United States since 1945, more than 60,000 have been disassembled by mid-2006. More than 13,000 of these warheads have been taken apart since 1990, but Energy retains more than 12,000 intact plutonium pits from dismantled warheads and stores them at Pantex.
Russia. Moscow has released very little information about the size of its stockpile, and its future plans are not known with a great deal of certainty. We estimate that since 1949 the Soviet Union/Russia produced some 55,000 nuclear warheads and that about 30,000 warheads existed in 1991 at the end of the Cold War. A few statements from Russian officials provide an occasional benchmark to help roughly calculate stockpile size and trends. But these statements typically lack detail, and the referenced dates are often ambiguous. In 1993, Victor Mikhailov, then minister of atomic energy, revealed that in 1986 the Soviet Union had 45,000 warheads in its stockpile. A decade later, Mikhailov said that nearly half of these warheads had been dismantled. [1]
The Defense Department and the CIA estimated that Russia dismantled slightly more than 1,000 warheads per year during the 1990s, though how firm those estimates were is unknown. Of the 16,000 intact warheads we estimate to be in Russia's possession today, around 5,830 are considered operational. Because Russia has removed warheads from its deployed and operational forces faster than it could dismantle them, there is a backlog of warheads awaiting dismantlement. The Moscow Treaty limits Russia's "operationally deployed strategic warheads" to no more than 2,200 by 2012, but its arsenal could shrink below this limit. Russia's production of new systems has been slow, and it is uncertain whether it can maintain such a large number of warheads because of limited resources and funding. Russia had previously pressed for a limit of 1,500 operational strategic warheads as part of the treaty, but the United States rejected this limit.
