A shopping list is a list of items needed to be purchased by a shopper. Consumers often compile a shopping list of groceries to purchase on the next visit to the grocery store. The list may be compiled immediately before the shopping trip or incrementally as shopping needs arise throughout the week. The shopping list itself may be a scrap piece of paper or something more elaborate. There are pads with magnets for keeping an incremental list handy on the refrigerator. Any magnetic clip with scraps of paper can be used to achieve the same result. There is a device that dispenses a strip of paper from a roll for use in a shopping list.Amazon.com: Shopping List Keeper (Satin Silver) (10″H x 4″W): Kitchen & Dining Some shopping carts come with a small clipboard to fit shopping lists on. Home computers enable consumers to print their own custom list so that items are simply checked off instead of written down or they can manage the list completely on the computer with custom shopping list software. PDAs eliminate the need for a paper list completely and may be used to aid comparison shopping. Online software exists to manage shopping lists from cellphone as well the web. Electronic commerce websites typically provide a shopping list online for repeat shoppers at the site. Incremental lists typically have no structure and new items are added to the bottom of the list as they come up. If the list is compiled immediately before use, it can be organized by store layout (i.e. frozen foods are grouped together on the list) to minimize time in the store. Preprinted lists can be similarly organized. Some studies show approximately 40% of grocery shoppers use shopping lists, while other studies show 61–67% use lists. Of the items listed, 80% were purchased. However, listed items only accounted for 40% of total items purchased. Use of shopping lists clearly impact shopping behaviour. “Written shopping lists significantly reduce average expenditure.” Use of shopping lists may be correlated to personality types. There are “demographic differences between list and non list shoppers; the former are more likely to be female, while the latter are more likely to be childless.” Shopping with a list is a commonly employed behavioral weight loss guideline designed to reduce food purchases and therefore food consumption. Studies are divided on the effectiveness of this technique. Remembering a shopping list is a standard experiment in psychology. There are surviving examples of Roman shopping lists.UK researchers have deciphered a Roman soldier’s shopping list using the latest virtual technology. The discovery is part of a project by Oxford University researchers to identify the markings on hundreds of Roman letters, contracts and other documents found in the 1970s by excavators at Hadrian’s wall – the most important monument built by the Romans in Britain. The documents were originally written in wax on wooden tablets but after 2000 years, the wax has degraded and all that remains of many of the scripts are faint scratches in the pieces of wood. Oxford historian, Dr Roger Tomlin deciphered one of the documents and found it to be a shopping list for a Roman soldier. It reveals that to buy a clothing outfit at auction, an average Roman soldier would have paid 8 percent of his yearly income (25 denarii). He would have had to fork out another 10 percent for a cloak to protect him from Britain’s hostile climate. In order to read the stylus marks on each tablet, the researchers managed to exaggerate the faint scratchings. Using virtual technology they eliminated the wood grain from the tablets. By using low, focussed light, they identified the scratches by analysing their highlighted edges and the shadows they cast. Next, the researchers aim to develop a computer program that will help them to assess the probability that certain scratches in the wood are particular letters, speeding up the time taken to read more tablets. The UK Science Museum is currently displaying part of an ancient Roman shopping list that dates from 75-125 AD, and examples of the pens that the Romans used. Collecting discarded shopping lists is a niche hobby.