Relational databases have dominated the data landscape for more than three decades. Emerging in the 1970s and early 1980s, relational databases offered a searchable mechanism for persisting complex data with minimal use of storage space. Conserving storage space was an important consideration during that era, owing to the high price of storage devices. For example, in 1981, Morrow Designs offered a 26MB hard drive for $3,599—a good deal compared to the 18MB North Star hard drive for $4,199 that had appeared just six months earlier. Over the years, the relational model progressed, with the various implementations providing more and more functionality.