They found that some thieves like disorganised or busy shops where they can blend into the background, while others use an accomplice to who can create a distraction.
Thieves in the UK, US, Canada and Spain often try to act like other customers by getting a basket, and examining products before pocketing them - often checking for security tags - or sometimes they buy a cheap item at the till to look like a normal shopper.
Professor Martin Gill said there was no easy solution to combatting the menace. He said: "Wherever you go, despite the fact that security is there, shoplifters know how to get around it."
He advised retailers to focus their security on the products which were most likely to go missing.
Nick Turner, who runs a Spar store in Southwell, Nottinghamshire, said he mainly spotted youngsters pocketing goods, adding: "We probably don't spot the professional thieves as they're so good at what they do."
Michael James, of Copplestone Stores in Crediton, Devon said: "We're lucky because we don't get shoplifting in the store, and anyone that we've had a problem with in the past, we don't let in."