In November, 1969, Strategic Arms Limitation Talks (SALT) begun. This was primarily due to the economic impact that nuclear testing and production had on both U.S. and Soviet economies. The SALT I Treaty, which was signed in May 1972, produced an agreement on two significant documents. These were the Anti-Ballistic Missile Treaty (ABM Treaty) and the Interim Agreement on the Limitation of Strategic Offensive Arms. The ABM treaty limited each country to two ABM sites, while the Interim Agreement froze each country's number of intercontinental ballistic missiles (ICBMs) and submarine-launched ballistic missiles (SLBMs) at current levels for five years. This treaty significantly reduced nuclear-related costs as well as the risk of nuclear war. However, SALT I failed to address how many nuclear warheads could be placed on one missile. A new technology, known as multiple-independently targetable re-entry vehicle (MIRV), allowed single missiles to hold and launch multiple nuclear missiles at targets while in mid-air. Over the next 10 years, the Soviet Union and U.S. added 12,000 nuclear warheads to their already built arsenals.