The effectiveness of the two sentences can be evaluated based on their clarity and the information they convey.
- The first sentence presents a statistic about book purchases, which highlights the scale of the book market.
- The second sentence provides a contrasting viewpoint by noting that authors receive only a small portion of the profits, which underscores the disparity in the book industry.
Considering both the information provided and their relevance to one another, both sentences serve a purpose, but they do so differently. Therefore, the best response is:
They are equally effective.