AP Geography Unit II Overview

Population & Migration: Why It Matters

Geography isn’t just about land and maps—it’s about people, and how they live, move, and change over time. In Unit 2: Population and Migration Patterns and Processes, we dig into the forces shaping where humans live and how they shift across space. This unit helps us understand real-world issues like aging countries, refugee crises, and urban booms. Let’s break down the core ideas, and see them in action in today’s world.

I. Population Growth & Structure

To understand population, we start with metrics. Crude Birth Rate (CBR) and Crude Death Rate (CDR) tell us how many births or deaths happen per 1,000 people. The Natural Increase Rate (NIR) is the difference: how much a population is growing (or shrinking) without migration. The Total Fertility Rate (TFR) shows how many kids, on average, a woman will have in her lifetime.

We also analyze population pyramids, visual charts showing age and sex structure. A wide base means lots of children (rapid growth). A top-heavy pyramid signals aging populations. These shapes help us calculate dependency ratios—how many non‑working (young + old) rely on the working‑age group. High dependency ratios bring challenges in healthcare, pensions, and education.

The Demographic Transition Model (DTM) is a BIG idea in this unit. It outlines how societies move from high birth/death rates to low ones as they develop, usually over four or five stages. Most developed countries like the U.S., France, Germany, and Japan are in Stage 4 or 5—meaning low birth rates, low death rates, and aging populations.

II. Migration: The Movement Factor

Migration is the permanent relocation of people from one place to another. It can be voluntary—like moving for jobs—or forced, like fleeing war or persecution. Migration is driven by push factors (conflict, poverty, climate disasters) and pull factors (safety, jobs, family).

Types of migration include interregional (between regions), intraregional (within the same region), and international(across borders). Key terms include refugees, asylum seekers, and internally displaced persons (IDPs)—people forced from their homes, often due to violence or environmental stress.

III. Geographic Models & Theories in Action

Two major models help us understand migration: Ravenstein’s Laws of Migration and Zelinsky’s Migration Transition Model. Ravenstein, a 19th-century geographer, observed that most migrants move short distances, often toward cities. He also noted that migration tends to occur in steps (rural → town → city), young adults are the most likely to move, and for every migration there’s often a counter-movement.

Zelinsky’s Model links migration patterns to a country’s stage in the Demographic Transition Model (DTM). In early stages, migration is mostly seasonal or rural-to-urban. As countries industrialize, international migration increases. Later, migration becomes more internal—like city-to-suburb moves. In the most developed stages, countries often attract migrants from less developed regions to fill labor shortages.

These models show that migration isn’t random—it follows predictable patterns tied to economic opportunity, development, and population change. Whether it’s someone moving to Los Angeles for work or fleeing conflict in Syria, the forces behind migration are part of a larger global system.

IV. Population Policies & Impact

Governments shape population through pro-natalist and anti-natalist policies. Pro-natalist policies encourage more births (think tax credits or paid parental leave), often used by aging countries like Japan or Germany. In contrast, anti-natalist policies, like China’s former One-Child Policy, aim to limit population growth.

In 2025, the United States experienced its first net decline in foreign-born population in over 50 years. Analysts attribute this to increased deportations and tightened immigration rules. (Pew Research) Critics warn this could shrink the workforce and slow economic growth. (Dallas Fed)

Meanwhile, some Middle Eastern countries, particularly in the Gulf region, continue to rely heavily on foreign labor but have begun tightening residency laws—impacting long-term population structure and migration trends.

V. Modern Migration Challenges

The United States has been central to global migration debates. In 2025, protests erupted across cities like Los Angeles over new deportation policies and reduced asylum protections. These policies targeted undocumented immigrants, including those who had lived in the U.S. for years, sparking nationwide debates about economic impact, cultural integration, and human rights. (Wikipedia)

In Europe, countries like France, Germany, and the UK have implemented strict border controls in response to increased migration from conflict zones, particularly in Syria, Afghanistan, and Iraq. These policies reflect growing tension between national security concerns and humanitarian obligations.

VI. Population Pyramids & Dependency Ratios

Population pyramids help visualize age and gender structure, revealing demographic challenges. A shrinking base (fewer young people) signals future labor shortages. An expanding top (more elderly) raises the dependency ratio—the number of dependents each worker supports.

Countries like Japan and Italy now face serious economic consequences from their aging populations. Meanwhile, the U.S., though aging more slowly, may follow a similar path without sustained immigration.

VII. Why This Unit Is Crucial

Unit 2 ties together major themes—population change, migration, government policy, and economic impact. From birth rates to refugee movements, this unit helps us see how humans shape geography—and how geography, in turn, shapes our lives.

As future geographers, understanding these patterns prepares you to analyze global trends, empathize with displaced communities, and think critically about the world you’ll inherit. Whether you’re studying the rise of mega-cities, aging societies, or global migration, Unit 2 gives you the tools to ask better questions—and maybe even design smarter solutions.