The world population clock is one unique clock. A clock that keeps track of the worlds population continuously.

It was the only clock so probably most of the population.

34,013,354: as of 02/24/2010 according to Canada's population clock.

Big Ben is a clock.

The population of the US is much much greater. The population of Canada is around 33 million (http://www.statcan.gc.ca/edu/clock-horloge/edu06f_0001-eng.htm) whereas the population of the US is around 306 million (http://www.statcan.gc.ca/edu/clock-horloge/edu06f_0001-eng.htm)