Age Verification and Public Adaptation: A Pre-Registered Synthetic Control Multiverse

Background 

In recent years, U.S. states have increasingly passed laws requiring websites that host adult content to verify users’ ages before granting access. These policies are part of a broader global push to regulate online platforms, particularly in areas related to youth protection and digital harms. Supporters argue that age-verification requirements are necessary safeguards for minors, while critics raise concerns about privacy risks, data security, and the potential impact on lawful adult access.

Despite the rapid diffusion of these laws—and the legal challenges to slow them—there is limited empirical evidence about their real-world effects on online behavior. Because the internet operates across state and national boundaries, enforcing state-level regulations can be difficult, and websites do not always respond uniformly to new laws. Some platforms implement age-verification requirements while others do not, creating uneven compliance across the online ecosystem. This dynamic means that users may face a choice between verifying their age on compliant platforms, shifting to non-compliant websites, or using circumvention tools such as virtual private networks (VPNs). This study examines how online audiences respond when an age-verification law is implemented, focusing on observable changes in digital traffic patterns following a state-level policy.

Study 

The study examines the implementation of a U.S. state-level age-verification law requiring users to verify they are over 18 before accessing certain pornography websites. To estimate the policy’s causal effects, the authors employ a pre-registered synthetic control design, constructing a counterfactual version of the treated state using data from U.S. states that did not implement age-verification laws during the study period. The analysis uses state-level Google Trends data across the U.S., allowing the authors to compare observed post-implementation search behavior in treated states to an estimate of what that behavior would have looked like had the policy not been enacted.

The study uses this search data to measure changes in queries for major adult content websites before and after the law took effect. The authors validate this measure by comparing Google search interest with SimilarWeb traffic data from 2020 to 2025, finding strong positive correlations between search volume and actual website visits for the platforms studied. Because Google Trends provides publicly accessible data, it allows the study to analyze behavioral responses to the policy in a transparent and replicable way.]

Rather than relying on survey responses, the study tracks observable behavioral changes in online search activity. The analysis focuses on search traffic for the two largest pornography platforms in the U.S., which rank among the top 20 websites in overall national web traffic. The key distinction between them is regulatory compliance: one platform implemented age-verification requirements in response to the law, while the other did not. This comparison allows the authors to directly assess how age-verification policies affect compliant versus non-compliant platforms.

Beyond measuring declines in searches for compliant websites, the study also examines potential adaptation strategies by users. These include increased searches for non-compliant platforms, VPN services, and adult content more broadly, which may signal attempts to circumvent verification requirements. To evaluate whether the findings depend on particular modeling choices, the authors conduct a pre-registered “multiverse” analysis, repeating the analysis across many reasonable specifications to test whether the results remain consistent.

Results 

The study finds that the implementation of age-verification laws led to a substantial and immediate decline in traffic to a major compliant pornography website in the treated state relative to its synthetic control. Three months after the law was passed, searches for the compliant platform fell by approximately 51%, indicating that the policy significantly reduced traffic to the site that implemented verification requirements.

At the same time, the results show clear evidence of behavioral adaptation. Searches for a major non-compliant platform increased by 48.1% over the same three month period, suggesting that some users shifted toward websites that did not implement age-verification systems. The study also finds a 23.6% increase in searches for VPN services, indicating growing interest in tools that can be used to bypass geographic restrictions or verification requirements.

Taken together, these findings show that state-level age-verification laws can harm compliant firms while shifting users toward less regulated corners of the internet, including non-compliant websites and VPN services. Rather than uniformly reducing access to adult content, the policy appears to redistribute user activity toward platforms that do not implement verification requirements or toward tools that help users bypass them. These dynamics highlight how users adapt to regulation and may help inform how policymakers approach this evolving area of digital content regulation.