Terrence Maxwell has a new article in First Monday (Is Copyright Necessary?) attempting to model the effects of different copyright policies historically and into the future (e.g. authors wanting high-protection copyright vs. the public wanting low-protection copyright). His models are fairly abstract and complex (see image below), but his results are interesting:

As indicated in the table, the desired policies of authors, publishers and public domain advocates produce very different outcomes in a 100–year simulation, some of which run counter to the protagonists’ stated goals. For instance, while the authors’ position led to the largest number of authors, it also generated the lowest sales figures, and the fewest number of volumes published. This indicates that the demand for new volumes from authors was the lowest among the three options, and points to a greater level of competition among authors seeking publication. Similarly, while the reader position generated the highest level of sales, the greatest number of different volumes, and the lowest cost for books, it also severely constrained the number of authors. This means that while a greater number of volumes would be available, diversity in authorship would be curtailed. This, in turn, would tend to diminish the likelihood of variety in information products.