the ridiculous state of shoe sizing

Comparing Lucky Brand and Birkenstock sizing shows that there is a problem: At Lucky Brand, 26 cm = U.S. Women's size 10 = Euro Size 41. i18nguy says Japanese women's 26 cm = U.S. Women's size 10 = Euro Size 42. Zappos says 25.9 cm = U.S. Women's size 10 = Euro Size 40-41. Wikipedia puts 26 cm = U.S. Women's size 9 = Euro size 40-41. I pretty reliably wear a U.S. Women's size 9.5. http://www.tobiasmayer.com/conversion.php