New NPG Paper Examines Why U.S. Population Continues to Grow Despite Smaller Family Sizes

• NPG
• September 11, 2025
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Why Smaller Families Haven’t Stopped U.S. Population Growth

Alexandria, VA, (September 11, 2025) – Negative Population Growth, Inc. (NPG) has published a new Forum paper, Why ZPG Did Not Achieve Its Goal to Lower Population and Why We Can’t Grow On Forever, authored by naturalist and author Dr. Karen I. Shragg. The paper explores the complex dynamics of U.S. population growth, questioning why the nation’s population has continued to rise despite a decades-long trend of American families choosing to have fewer children.

Shragg’s work revisits the Zero Population Growth (ZPG) movement of the 1970s, which successfully encouraged many Americans to have smaller families with the goal of stabilizing U.S. population to protect the environment. The paper reveals that while the national birth rate has fallen, the U.S. population has grown by nearly 140 million people since 1970, undermining the collective benefits of smaller families. Shragg notes: “Our cities are more crowded, our roads are more clogged, our National Parks need reservations months in advance and housing is in such great demand that only the very rich can compete in an inflated housing market.”

Shragg pulls no punches as she quickly identifies mass immigration as the primary driver of this continued growth, challenging the notion that a smaller U.S. population can be achieved solely by focusing on birth rates. She advocates for immigration policy to be part of the broader discussion on environmental conversation. “Many argue that immigration doesn’t matter because the overall population of the world remains the same. True enough, but keeping limits on growth is a local challenge—best addressed with local laws and enforcement. The US cannot be the release valve for other countries.”

For research purposes, Shragg asked some individuals from her personal network to answer some population-related questions. Three respondents “felt that they hadn’t made any real sacrifice with their small family decisions.” The response from a Minnesota couple was different. They were directly involved with the ZPG movement and were strongly influenced by Paul Ehrlich’s The Population Bomb. The couple shared: “We hoped that through public education people would be motivated to limit family size voluntarily. We recognize that population size as well as per capita consumption are at the root of environmental problems. What we didn’t recognize at the time was the role that immigration would ultimately play in the continued growth of U.S. population.”

Why ZPG Did Not Achieve Its Goal to Lower Population and Why We Can’t Grow On Forever urges environmental organizations, policymakers, and the public to adopt a more comprehensive approach to sustainability. It calls for a renewed focus on both family size and immigration as key components of a responsible national population policy. Dr. Shragg concludes: “The messaging on all environmental and quality-of-life issues, from saving wildlife to preventing water scarcity and climate change, must include small families and sensible immigration policy focused on sustainability.”

Since 1972, NPG has worked to educate both the public and policy leaders about the impacts of overpopulation. With a steadfast commitment to reducing population growth to achieve a sustainable balance with our environmental resources, NPG continues to be a leading voice of reason in a world often driven by the pursuit of perpetual growth. NPG advocates for the adoption of its Proposed National Population Policy, with the goal of eventually stabilizing U.S. population at a sustainable level – far lower than today’s. We do not simply identify the problems – we propose solutions.  For more information, visit our website at NPG.org, follow us on Facebook @NegativePopulationGrowth or follow us on X @npg_org.