"five nines": purity (1961), reliability (1992)

Benjamin Zimmer bgzimmer at RCI.RUTGERS.EDU
Sat Apr 9 07:49:04 UTC 2005

>From Slate ("What Can Bloggers Do That Reporters Can't?" by Jack Shafer,
April 8, 2005):

While not five nines reliable, the better blogs that I read are as
accurate as your average daily newspaper (which might not be saying that

Shafer is extending the expression "five nines" -- referring to a goal of
99.999% reliability -- from its usual context of networking or
telecommunications systems.  One article ("Reality Check On Five-Nines"
<http://www.bcr.com/bcrmag/2002/05/p22.php>) claims that "everyone in
telecom has been using the term 'five-nines' for decades."  I can find
"five nines" back to 1961 in references to chemical purity, but only to
1992 in references to reliability.

1961 _Physical Rev._ 121 1640/2 "Five nines pure" Ga<sub>2</sub>
O<sub>3</sub> was obtained from Eagle-Picher and "five nines pure"
Y<sub>2</sub>O<sub>3</sub> was obtained from Lindsay Chemical Company.
1965 _Physical Rev._ 137 1237/1 This would indicate an impurity
concentration of 1x10<sup>-5</sup>, i.e., the Cu was of "five nines
1992 _InformationWeek_ 23 Mar. 56 (Nexis) FAA targets the 'five nines' --
Network undergoes overhaul to achieve 99.999% reliability. ... The Lincs
contract sets a number of precedents, the FAA claims. It virtually
eliminates a single point of network failure by guaranteeing 99.999%
availability (the "five nines" are a networking holy grail).
1992 _Wall St Journal_ 29 Sep. B4 (Proquest) Every time Stratus Computer
Inc. President William E. Foster shows off a new computer, he opens up its
cabinet and yanks out a wire or a circuit board. It keeps on humming.
That's "five-nines engineering," he explains, meaning 99.999% reliability.

--Ben Zimmer

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