On Fri, 06 Nov 2009 06:28:37 GMT, "William R. Walsh"
m wrote:

Or perhaps it is in the page coverage percentage. Printer makers express
toner cartridge life at a given % of coverage on a page. I think the usual
figure is based on a 10% coverage.

HP originally used 5%. That resulted in yields for US and EU being
slightly different due to the differences between letter size and A4
size paper. Since 2004, everyone uses ISO/IEC 19752.

More on how page yield is measured:
http://www.hp.com/pageyield/articles/us/en/MonoLaserJetYieldArticle.html
http://en.wikipedia.org/wiki/ISO/IEC_19752

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Jeff Liebermann
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