Read this: Depending on a number of considerations, a company may apply for and be granted a patent for the drug, or the process of producing the drug, granting exclusivity rights typically for about 20 years. However, only after rigorous study and testing, which takes 10 to 15 years on average, will governmental authorities grant permission for the company to market and sell the drug. Patent protection enables the owner of the patent to recover the costs of research and development through high profit margins for the branded drug. When the patent protection for the drug expires, a generic drug is usually developed and sold by a competing company. The development and approval of generics is less expensive, allowing them to be sold at a lower price. Often the owner of the branded drug will introduce a generic version before the patent expires in order to get a head start in the generic market. Restructuring has therefore become routine, driven by the patent expiration of products launched during the industry's "golden era" in the 1990s and companies' failure to develop sufficient new blockbuster products to replace lost revenues.

What decade was the pharmaceutical industry's "drug era"?
What is the answer? (If it cannot be answered, return "unanswerable")
unanswerable