Objectives: In this paper, we attempt to quantify the "echo" effects of the downward shock in US smoking prevalence from mass education starting about 1965 through 2010. Methods: An agent- based population simulation replicates the observed effects of the initial education shock on smoking prevalence, and then estimates ongoing echo effects based on empirical estimates of the effects of parental smoking on initiation and peer-group quitting contagion. Further simulations estimate what additional echo effects would explain the entire historical reduction. Results: About one-third of the observed prevalence decline through 2010 can be attributed solely to fewer parents smoking after the initial education shock. Combining peer-group cessation contagion explains well over one-half of the total historical prevalence reduction. Plausible additional echo effects could explain the entire historical reduction in smoking prevalence. Conclusions: Ongoing anti-smoking interventions are credited with ongoing reductions in smoking, but most, or perhaps all that credit really belongs to the initial education and its continuing echoes. Ensuring that people understand the health risks of smoking causes large and ongoing reductions. The effect of all other interventions (other than introducing appealing substitutes) is clearly modest, and quite possibly, approximately zero, after accounting for the echo effects.