Do author blogs cause book sales?

It’s a question we self-published authors often ask ourselves. Is anyone reading my blog actually buying my books? Of course, we get anecdotal confirmation when a commenter  mentions that they bought a book. But, statistically speaking, is there a correlation between blogging and sales?

I’ve already posted three times (here, here, and here) about paid advertising. I thought I should pontificate on non-paid advertising, which is what this blog is. Aside from a place to wax endlessly about charts and writing, this blog is also here to get people interested in my books. But, is that working?

Here's another spiffy chart to try to answer that question:

In the chart, the white line indicates daily views on this blog. The red line is the daily total sales of all my books. While the height of the two lines can differ significantly, there is definitely a correlation with the peaks and valleys.

Between 12/27/2010 and about 1/3/2011, the blog line seems to lag behind the sales line. Does this indicate readers who first bought my book, then found my blog? One can assume that.

But, things seem to turn around 1/5/2011. There, it looks like the blogviews and sales lines get in sync. A sales peak matches a blog peak, and the valleys line up, too.

I never expected there to be this much of a correlation. It looks like my blog is helping sales!

Or is it?

The peaks and valleys are usually right on the same day, so there is no definitive way to determine if the book caused the blogviews, or the blogviews caused the book sales.

However, since it takes more effort to get to my blog from my book, I think it’s safe to assume that the causality here is probably from blog views to book sales.

So, my advice to other authors is to start and maintain a blog. You’ll probably get more sales as your blog becomes more popular.