Confirmation bias is one of the biggest problems in investing. We all have a set of core beliefs, and we tend to surround ourselves with people who also believe them and focus on information that validates them.

For me, one of those things is that value stocks will beat the market over time.

There is no shortage of data to support value. The academic research shows that is has worked historically. And the work of practitioners like AQR, Research Affiliates and O’Shaughnessy Asset Management does the same.

But there is a danger in following only the people and data who support what you believe. It can blind you to the other side of the argument, especially when your beliefs are strongly held. And there is almost always another side.