their users a range of options. With consumer concern about climate change growing, a number of green rewards shopping portals have appeared. Instead of cash back or points these websites offer carbon credits (also known as carbon offsets) or green gadgets to encourage consumers to shop with particular retailers or make changes to their lifestyle. Criticisms Points-based web sites may have different currencies, which makes it difficult to compare the customer benefit. Most reward websites retain a proportion of the commission, and only industry insiders are aware of the nuances of the business model used and therefore the customer benefit. From the consumer's perspective it may not always be clear whether the benefit going to the supported cause is the most effective way of raising funds. For example, in some countries like the UK, a significant tax benefit can be provided to the charity by donating in cash. While the majority of green reward websites also offer some useful information and advice on greener living, few of them seem to encourage more sustainable consumption. See also Affiliate marketing Loyalty program Sales promotion Frequent flyer program References Online advertising Reward websites