that, despite the nominal rise in the cost of a first-class stamp, the adjusted cost of a stamp has stayed relatively stable. Since at least the early 1980s, the price of a stamp has closely followed the consumer price index. The large jumps in the early 1900s are because a change by a single penny was large compared to the cost of the stamp. For example, the price increase from $0.02 to $0.03 on July 6, 1932, was a 50% increase in cost. Additionally, while the cost of the stamp itself remained fixed, the adjusted price in 2019 dollars was not fixed over time which added to larger jumps in adjusted prices. Historical notes Domestic parcel post service was adopted in 1913, 25 years after the Post Office had agreed to deliver international parcel post packages pursuant to the Universal Postal Union treaty and various bilateral agreements with other nations: Initially, few if any postal regulations governed packages mailed by parcel post. For example, to construct a bank in Vernal, Utah, in 1916, a Salt Lake City company ascertained that the cheapest way to send of bricks to the building was by parcel post, and the company proceeded to do so. For another example, Charlotte May Pierstorff, then a five-year-old, was mailed via parcel post in 1914; she survived, but the regulations were clarified to prohibit the use of parcel post for human transport. Bulk postal rates were restructured in 1996: Second Class became Periodicals Third and Fourth Class Mail became Standard Mail (A) and (B) Special Fourth Class Mail was renamed Special Standard Mail In 2007, First Class Mail was restructured to include variable pricing based on size, not just on weight. Shape-based postage pricing is a form of dimensional weight. Also at that time, International Parcel Post air service was re-branded as Priority Mail International, and Parcel Post surface service was discontinued for international destinations. Regular Air Mail service began in 1918 and over the years rates varied considerably depending on distance and technology. Domestic Air Mail, as a class of service, officially ended May 1, 1977. By that time all domestic First Class Mail was being dispatched by the most expeditious means, surface or air, whether or not the Air Mail postage had been paid. Additional charges for Special delivery existed from 1885 to 2001. Today, Express Mail Overnight is the most similar service level. During the