We're getting reports about increases of theft in shops and malls. Most shops and malls can't afford elaborate anti-theft systems so the best recourse is to pay attention to your customers, particularly ones you don't know. Many times the layout of the shop/mall makes that difficult particularly with limited staff. In that case, make sure your most valuable items are under lock and key.
Other things to consider is posting a sign at the front door stating "NO LARGE BAGS IN STORE," and enforcing the policy. A favorite trick of shoplifters is working in teams as one thief distracts a clerk and the other steals. If there's more than one person working the store, don't get caught with both clerks helping one customer. If alone, a good policy is not to leave the counter behind the front door, therefore watching who comes and goes, and if someone has a question, have them bring the question to the clerk.
Times are getting easier so be wary of unfamiliar faces. If you've got some ideas on preventing theft, comment back. And, of course, talk to your local police force about other prevention measures to take.
