80/20 Rule

Numbers alone must not be the driving factor for technology decisions. Both mainstream (80/20) and edge-case requirements must be addressed, because for online information, there is:

1. No standardized user, and
2. No standardized device (browser or other user agent) for accessing information.

Longdesc usage is not and will never be widespread because:

• People with disabilities are a minority.
• Images that need longdesc are a minority.

As Al Gilman said a few years ago,

80%-rule-NOT

Some commentors have suggested that in order to sustain a small language there have to be some screening factors, and frequency of use in the as-is Web is the screening factor to use.

The WAI position on this is roughly "that is like saying that the builder of a high-rise building should decide whether or not to include fire-stairs based on whether the previous buildings at that street address had burned down or not."

We don't build fire stairs just enough to evacuate 80% of the occupants.

Accessibility features address failure modes that are infrequent, but critical when they occur.

Popularity among authors should be used to select between _functionally complete_ alternative strategies for supporting required functionality.