REX BRIGGS, MARKETING EVOLUTION: It's amazing that it's
taken this long for marketers to wake up and go, "Wow, 15 per cent of our consumers' time is being spent on the Internet and yet we barely have a presence there in terms of advertising."
MARTIN HOFFMAN, NINEMSN: We're still only at less than 4 per cent of marketing dollars being spent there,
so the catch-up between those two forces is what's driving the growth.
I don't understand the highlighted sentence with blue color. What's the 'two forces' means here?
Thanks