the world of partworks is a very secretive part of the world of journalism. They sell generally on subscription, and usually shops dont stock 'em after the first few issues, but they continue to sell to those who bought the first three parts of HMS bounty (or whatever) and now want to complete it in just 1,000 weeks.
The number of people who buy them is not generally known as they don't have to make their circulation figures public as they don't have any advertising. this partialy explains why they're so damn expensive.
It also seems that those who subscribe don't generally let their mates know about their partwork affliction.
Incidentally, they tend to be launched in January (this year the prisoner, gods of ancient egypt, christ knows what else all hit the market) to coincide with people's plan to do something worthwhile and make something of themselves. In easy to consume weekly parts.
The market for partworks is, strangely, almost entirely sewn up by Italian based companies.
Now...when do they plan to launch the Taggart partwork....
*value of posts can go down as well as up.