There has been a clear trend over the past 40 years to running shorter-length TV commercials.

In 1965, 77% of all US network TV commercials lasted 60 seconds, a share which dropped to 27% five years later and has since fallen to 7% (2004).

30-sec ads made up 23% of the total in 1965 and 72% in 1970, but fell back to 56% in 2004. 15-sec units, introduced in the late 1980s, made up a third of all messages by this date.

In the UK, similar trends towards downsizing spot lengths have been apparent. 30-sec ads already made up two-thirds of the total by 1972, while those lasting 15 secs represented a further 20%. By 2005, 30-sec spots constituted 45% of the UK total, 15-sec ads had virtually disappeared and 10- and 20-sec spot lengths each made up around one fifth of the total.