EDIT Per one thousand, or a thousandth. One-tenth of a percent.

See also
% U+0025 PERCENT SIGN,
٪ U+066A ARABIC PERCENT SIGN,
⁒ U+2052 COMMERCIAL MINUS SIGN,
‰ U+2030 PER MILLE SIGN
‱ U+2031 PER TEN THOUSAND SIGN.

 jsw