Anyone who has ever wasted hours trawling through a book shop only to eventually be told 'we don't actually stock that title' will agree that despite what they may claim, the choice of stock offered by most shops is actually very limited. Of course shops that stock a wide variety of different things (such as supermarkets) will only be able to offer a small selection of each product. You are, for example, not likely to find a comprehensive selection of the thousands of different species of edible mushrooms in the 'fresh fruit and veg' section of your local supermarket. Yet as the above example of familiar book shop frustrations demonstrates, we often find that even shops specialising in one particular product frequently fail to stock the specific item that we are looking for. How many of us have walked out of shoe shops without a new pair of shoes in our hand? That will be everyone then.

As inconvenient as this limited choice can be, however, the reason behind it is both practical and understandable. Real 'bricks and mortar' shops - even those that specialise in a particular product - can only offer their customers a small selection of products because they can only hold a finite number of stock. When you then think of the number of books in the world compared to the size of your average book shop, it really is no wonder that you often will not be able to find the title you are looking for! As a result of this inability to stock a large variety of products, it is of course in every shop's financial interests to primarily stock items that are known,or can reasonably be predicted to sell well. If using a bookshop again as an example, it is then for this reason that you will generally only find each author's most famous and/or most recent titles stocked and why you will always be able to buy a copy of Harry Potter!

However, this principle of stocking only 'best selling' items simply does not apply to online stores and it is here that Chris Anderson's 'long tail' theory comes into play. Unlike regular shops, online shops are not limited in the amount of stock they can list as being for sale, which means as well as offering their customers generically popular items such as recently released Hollywood blockbusters and best selling novels, they can also offer obscure old black and white films and unheard of books by little known authors. They will obviously not sell as many of these niche products as they will 'best selling' ones, but if you stock a vast variety of niche products and only sell a few of each of them, you will end up making a rather tidy profit (just look at Amazon!).

Chris Anderson's so-called 'long tail' then refers to a graph that any online store might produce of all of its available products, starting with the best selling items on the left and moving over to the lowest sellers on the right. On such a graph you would see that a small number of the products on the left sell extremely well, but as you progress to the right the line gradually drops, levelling out at items that sell in low numbers. This kind of graph is therefore referred to as a 'long tail' graph, as the number of high-selling products is very short, whereas the number of products selling in smaller numbers is extremely long, yet increasingly more profitable.