The average UK internet user was aged 37.9 in Oct 2007, up from 35.7 at the same time the year before, according to Nielsen Online. The research firm estimates that the proportion of the UK internet population that is under 25 fell over the year, from 29% in Oct 2006 to 25% a year later. At the same time, the number of Britons over 55 using the web has grown substantially: 19% of the internet population came from the over 55 age group in Oct 2007, which represents year-on-year growth of 22%. Alex Burmaster of Nielsen Online says: "Age compositions tend to evolve subtly over a number of years, so to see such large changes in the course of just a year shows that the internet population is undergoing a significant ageing process." Burmaster believes this shift will have an impact on how marketing and ad money is spent online, saying: "New online offerings and technology are usually targeted at the young, but it's possible brands could be missing a trick if they continue down this path in the future."