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This is an industry wide problem and not unique to the Canary Islands because of two simple facts, langauge, most police do not speak other languages (and tourists do not speak the local language ) and secondly the victims are not around for the court prosecution should / when it eventually comes to court.
The only practical answer to this is greater local policing, but like all police forces they can only act on information they clearly understand.
So you are urged to report the crime to help the police aggregate figures, and if you have insurance and wish to claim you will need a reference number from the police to ensure your claim is successful.
UPDATE
We have learnt from the Canary NewsPaper that the Spanish Police are now about to participate on Twitter, this may be a significant opportunity for both parties to discuss problems such as petty theft that affect thousands of tourists to Gran Canaria each year.