Black smoke indicates that votes have been cast, but no candidate has received the two-thirds majority required to be elected pope. White smoke means that a new pope has been selected.

The Pipe Tobacco Council, an industry group, estimates 52 million pounds of pipe tobacco were sold in the United States in 1970. Last year, the figure was 7.1 million pounds, a decline of 86 percent.

It wasn't clear whether grey smoke was closer to black or white, for example. By the 1970s, the straw method had been abandoned in favour of more controllable chemical mixtures .