Between 1994 and 2000 cell phone use jumped from 1 percent to 10 percent of population. In the late 1990s Japan boast the world's highest per capita rate of cell phone ownership. About 37 percent of the population has a cell phone in 1999, compared to 25 percent in the United States.
By 2002, 50 percent of the population had a cell phone. Sales reached 50 million a year in 2003 when cell phones with cameras became widely available.
How does this concern fanfic writing?
the cause:
- Ranma 1/2 was completed before the cell phones became widespread.
- Sailor Moon was completed before the cell phones became widespread.
the effect:
- your plot looks more holey in the places where a simple phone call would significantly change it. Mainly, it's the great difference between the todays ability to instantly connect to someone you know the number of vs the much greater disconnectedness of people in the before-cellphone era. When you can talk to someone (or know if they are even alive) only if you meet them or call their home (because phone numbers tie you to homes, not people). Imagine how the Herb story arc would change if both Ranma and Akane had cell phones (well, Ranma could've broken his in the final battle, but still). Imagine how much would having cell phones rearrange the entire plot of R1/2.
- you *have* to borrow the PGSM premise of magical cell phones replacing both communicators and henshin pens if you place your story later than, say, 1996..2000. In other words, the "eternal summer" or "eternal present" both Rumiko Takahashi and Rebecca Heineman are so fond of fails plunging face-first into this trope.
After making this research, I had to draw a line and state explicitly that my fic takes place "in the late 1990-s".