Frequency
Frequency
[Repetitive events are written in grey and arranged in a grid. Each statement pulses to black and then returns to grey at an interval characteristic of the named event.]

This comic shows a number of common events, arranged in a grid. Each of the events flashes with its average frequency.
For example, statistically a child is born somewhere on the world approximately every 0.24 seconds, or four times per second. Therefore, the tile "One birth" blinks about 4 times per second.
The title text refers to the Pitch drop experiment which measures the flow of a piece of pitch over many years. At room temperature, tar pitch flows at a very slow rate, taking several years to form a single drop. The title text jokes that Randall tried to include a tile that flashes about once every ten years , but the tiles are all animated GIFs and while the file format supports animations of any length, the resulting file would be too big (at least 10 megabytes).
A thorough analysis of the frequencies present in this comic and how they relate to the underlying technology (the GIF format) was published as Reverse Engineering xkcd's 'Frequency' .
The table below lists all the events and their duration / frequency. Some events make reference to other comics.
[Repetitive events are written in grey and arranged in a grid. Each statement pulses to black and then returns to grey at an interval characteristic of the named event.]
