A spate of deals on Thursday showed that health care companies are convinced, regardless of tax benefits, that bigger is not only better, it is necessary.

The whole industry seems to be reading from the same playbook: Pair up with a company that makes the same product to become a leading provider, and thus gain more clout to negotiate business with hospitals and health insurers.

That explains some of the impetus behind the more than $40 billion of deals announced on Thursday. Some of the deal activity can also be explained by the desire to acquire growing biotech firms and product lines to make up for older products whose sales are in decline.

To get bigger in the cardiovascular-device world, Abbott agreed to purchase St. Jude Medical for $25 billion. To double down on treatments for prostate cancer, Sanofi made an offer to buy Medivation for about $9.3 billion. And as part of a bigger push into oncology treatments, AbbVie signed a $5.8 billion deal for Stemcentrx.