A bed manufacturer Paramount Bed researched people's naps in 2008. According to it, 26.3% of Japanese people take daytime naps regularly. These statistics do not include babies' naps.
Figure 1: Ratio of people who take naps (n = 1450)
Among the people who take naps, the average sleeping time was 40 minutes.
Figure 2: Sleeping time of a nap among the people who take naps (n = 381)
Personally, I was surprised that such so many people have naps. My lunch break is only 60 minutes long. How do they manage their time?
Source is Paramount Bed, www.paramount.co.jp/