The most in the world, apparently.
Reasons for that statistic include:
1. Many of those newspapers are actually bought by offices (including, strangely, some offices where being seen reading them would be completely unacceptable…)
2. Most statistics include the thinner and cheaper evening editions
3. Many Japanese don’t read for pleasure*, leaving a newspaper the obvious thing to read
4. Really heavy sales tactics by the newspaper delivery salesmen
5. Many Japanese would be embarrassed by everyone being able to judge their political position by seeing what paper they read in public, so regular home delivery is the only solution
6. Most Japanese access the internet on their mobile phones rather than through PCs, making reading of full news articles a bit inconvenient (when possible)
7. TV news is dull and says nothing (NHK) or sensationalist and says nothing (all the rest, e.g. Fuji Terebi), so a newspaper is your best chance of getting some slightly deeper and more even handed coverage
8. It provides some conversational ammunition, the Japanese generally being even worse conversationalists than the British and so desperate for things to speak about
9. Extreme negative reactions to not knowing things that others consider general knowledge
*“a 32-country survey… showed Japan to be the country with the highest number of middle and high school students reporting that they did not read for pleasure” Language and Society in Japan pg 94