These stats are hard to interpret - this could all very well be consistent with the kids these days turning out to be the most literate generation in history. There is very strong incentive to get good at reading to interact with the internet even if it isn't reading for 'enjoyment'.

There is a linked PDF, but I'd actually be more interested in reading the original survey to see how 'reading' is being framed. Is an hour in the HN comments section counted as reading for fun?