Investing in legal advice

I study the effect of strategic product market considerations on the resource spending decision of plaintiffs in patent lawsuits. I use a unique sample of US patent litigation cases and focus on an important decision of the plaintiffs; their decision to hire external attorneys. I find that plaintiffs hire significantly more attorneys if they are in a horizontal relationship with the defendant rather than in a vertical relationship, i.e., if the litigants compete on the product market. This strategic product market effect is more pronounced the more concentrated the product market is.