UK Internet Stats: Internet Users Count Doubled In The Last Six Years

This is a stat which sounded a little strange, given the fact that we are talking about 2006 to 2012 and not some time in the late 90s - we spotted this stat today, that in 2012, 33 million adults used the internet daily in the UK, compared with 16 million in 2006 (Source)

How do we digest this number? Is this any kind of anomaly, like the Google's UK Revenue anomaly? We don't know that, but such a rate of growth, for a developed country, for such a basic parameter, coming in the second half of the decade is a little surprising.