Period 9 runs from 1980 to the present. It is short in topics but wide in scope, and the exam treats it as the culmination of arguments running through the whole course: the size of government, the country's global role, and who counts as a full member of the nation.

The conservative movement 保守主义运动 that organised in the 1960s and 1970s came to power with Ronald Reagan 里根. Its programme had three strands:

• Tax cuts and deregulation 减税与放松管制, on the argument that reducing the burden on business would raise growth - often called supply-side economics 供给学派经济学.
• Reduced federal spending on domestic programmes, though defence spending 国防开支 rose sharply and deficits grew.
• Appeals to social conservatism 社会保守主义, on religion, family, and law and order.

The result was a lasting shift in the terms of debate: after 1980 both parties argued within narrower limits about the federal government's economic role than at any time since the New Deal.

Renewed military build-up, negotiation, and above all internal weakness in the Soviet Union brought the Cold War to an end. The Soviet system collapsed between 1989 and 1991.

The consequences framed the decades that followed: the United States became the sole superpower, with unresolved questions about when and where to intervene 何时何地干预, and about what commitments made sense once containment no longer organised policy.

The economy after 1980 was reshaped by three forces:

• Globalization 全球化 - trade agreements, integrated supply chains, and competition that moved manufacturing abroad.
• Deindustrialization 去工业化 - the loss of manufacturing employment in older industrial regions and the growth of service work.
• Technological change 技术变革 - computing and then the internet, which transformed productivity, work, and communication.

Together these raised aggregate wealth while widening income inequality 收入不平等 and reducing security for workers whose industries declined - the economic argument that has dominated politics since.

Migration and immigration 人口迁移与移民 in the 1990s and 2000s continued to reshape the population, with growth in arrivals from Latin America and Asia 拉丁美洲与亚洲 following the 1965 reform of immigration law.

The consequences are the examinable part: population growth in the South and West, the growth of multi-ethnic cities, ongoing debate over immigration policy 移民政策 and border enforcement, and continuing arguments about citizenship 公民身份 and national identity - the same argument the course has traced since Reconstruction.

The period's later topics group around a small number of developments:

• The September 11 attacks 九一一袭击 and the response - military intervention abroad, a new security apparatus, and renewed debate over the balance between security and civil liberties 安全与公民自由.
• Economic crisis in 2008 and the argument over government's role in stabilising the economy.
• Political polarisation 政治极化, amplified by changes in media and communication.
• Debate over climate and energy 气候与能源 policy.

The period's reasoning skill is causation, and the most useful move is to link a recent development back to an earlier one: deindustrialisation to the market revolution's regional specialisation, immigration debates to the nativism of the 1850s and 1920s, and arguments over federal power to the New Deal.

Worked example (a real AP exam question). The 2026 exam set the long essay "Evaluate the extent to which women's participation in public life in the United States changed" over the twentieth century. A strong thesis distinguishes kinds of change and their timing: "Women's participation in public life changed substantially across the twentieth century, as suffrage, wartime employment and the women's movement opened political and professional roles, although occupational segregation and unequal pay meant participation expanded faster in law than in economic power." Notice the shape: for a long-span prompt, the thesis must say what kind of change and where it stalled, since that is what allows evidence from several periods to be used rather than narrated.

• Define supply-side economics as an argument (cut taxes to raise growth), and note the deficits that followed - both belong in an evaluation.
• The Cold War's end matters for what it opened: sole-superpower status and unresolved questions about intervention.
• Keep globalization, deindustrialization, and technological change as three distinct causes, not one blur.
• For immigration after 1965, name the shift in origins and the political argument it produced.
• After 2001, the examinable tension is security against civil liberties - the same tension as the Red Scare and the First World War.
• Long-span prompts reward connecting periods. Link a recent development to an earlier one and say what continued.