In his comments section he estimated it was a percentage in the single digits... http://krebsonsecurity.com/2015/09/tracking-bluetooth-skimmers-in-mexico-part-

In his comments section he estimated it was a percentage in the single digits... http://krebsonsecurity.com/2015/09/tracking-bluetooth-skimmers-in-mexico-part-ii/comment-page-1/#comment-392856 http://krebsonsecurity.com/2015/09/tracking-bluetooth-skimme...