Pfizer (PFE) announced Monday it will buy Allergan (AGN) for $363.63 a share, or about $160 billion in the biggest deal ever in the health sector. The transaction will allow the New York-based drug giant to relocate to Ireland to cut its U.S. tax burden. The deal represents a premium of over 30 percent based on the companies' unaffected shares price as of Oct. 28, Pfizer and Allergan said in a joint statement. "Through this combination, Pfizer will have greater financial flexibility that will facilitate our continued discovery and development of new innovative medicines for patients, direct return of capital to shareholders, and continued investment in the United States, while also enabling our pursuit of business development opportunities on a more competitive footing within our industry," Pfizer Chief Executive Ian Read said.  Allergan shareholders will receive 11.3 shares of the combined company — Pfizer PLC — for each Allergan share, while current Pfizer shareholders will receive one share of the new company for each share they own. Read more at CNBC.