America's decades-long anti-tobacco effort has yielded massive benefits, cutting the smoking rate in half since 1964 and saving untold millions of lives. But the smoking rate has plateaued in recent years, at around a fifth of U.S. adults.
Has policy reached its limit? Will there always be a chunk of the population that cannot resist lighting up or chewing?
Federal, state and local governments have not given up. Congress in 2009 gave the Food and Drug Administration authority to regulate tobacco; the agency could eventually require reductions of addictive chemicals and carcinogens in tobacco products.
Federal rules now prohibit flavored cigarettes and misleading terms on packaging such as "low," "light" and "mild." Many - but not all - states have adopted smoke-free policies in bars, restaurants and workplaces. And some states have continued to crank up their most effective weapon: tobacco taxes, which encourage quitting and which have a particularly good record at preventing teen smoking.
But raising taxes can also spur the development of a black market, as shown by tobacco smuggling - where cigarettes are taken from states with low tobacco taxes into those with higher ones.
No doubt much of this problem could be solved by raising the federal tobacco tax with an eye toward harmonizing state policies.
But how far even the federal government can increase its excise without inviting international smuggling or other illicit commerce is an open question.
New Zealand may help provide an answer. The Pacific nation announced last week a pathbreaking plan to eliminate smoking by 2025.
Among other things, shops selling cigarettes will have to conceal them from view. New Zealand will increase its already high tobacco tax by 40 percent, bringing the price of a pack to about $15 (U.S.).
That's a few bucks higher than packs in New York City, which has the highest cigarette taxes in the United States. But New Zealand's is also a national policy, so criminals will find it harder to supply illicit tobacco there than they do in America's high-tax areas.
There is a point beyond which raising national cigarette taxes stops being useful, or becomes a prohibition policy in all but name. New Zealand considered and rejected the idea of raising the price to $75 a pack.
But $15 a pack may discourage use further without eliminating individual choice. After 2016, when the country's new policy phases in fully, public-health advocates will have additional evidence one way or another.