Many firms advertise their goods or services, but are they wasting economic resources? Some economists reckon that advertising merely manipulates consumer tastes and creates desires that would not otherwise exist. By increasing product differentiation and encouraging brand loyalty advertising may make consumers less price sensitive, moving the market further from perfect competition towards imperfect competition (see monopolistic competition) and increasing the ability of firms to charge more than marginal cost. Heavy spending on advertising may also create a barrier to entry, as a firm entering the market would have to spend a lot on advertising too. However, some economists argue that advertising is economically valuable because it increases the flow of information in the economy and reduces the asymmetric information between the seller and the consumer. This intensifies competition, as consumers can be made aware quickly when there is a better deal on offer.