In the early 1990s, US export controls that aimed to keep high-tech goods and technologies out of the hands of enemies deterred from $15 billion to $25 billion of such exports. Recent US export controls seem to deter US high-tech exports considerably less. As percentages of seven broad industrial categories of high-tech exports, estimated American export shortfalls from national security controls have fallen from roughly 5 percent in the early 1990s to slightly over 1 percent in the mid-to-late 2000s. Ongoing reform of American national-security export controls would seem to have only modest effects on the level of US high-tech exports. American exporters seem to have developed a distinctive competitive ability to shift their sales efforts flexibly among customers and products that are subject to tight, loose, and few controls. Important importing countries seem to have developed a distinctive ability to shift their sourcing flexibly among alternative suppliers, including a growing set of emerging exporters of high-tech goods. They are, however, still denied half of their potential high-tech imports from the ten exporters from which the authors draw their estimates.