When we talk about "diversity", we are referring to the "diversity of voices" that are desirable and maintain a variance in community standards around the country. However, diversity is often hard to define because it goes hand-in-hand with the First Amendment. Regulating content directly affects diversity on the air because if you regulate who has space on the spectrum, and how people make programming on this spectrum, the different types of programming that appears on the air is going to be affected.
To serve the public interest would be the easiest way of defining diversity, but the audience viewing patterns do not always provide the means for diverse voices. Diversity has value, and when determining what diversity is and how much diversity is enough often does not create "the range of program choices that encompasses many different types of programs". The desire for diversity on the airwaves is about choice for the audience, and without diversity, the audience is limited in the number of choice, in which all are not of interest. Providing a diversity of viewpoints through broadcasting has been a central part in the "public interest, convenience & necessity", but the regulating structure is often ineffective in providing content diversity.
In the example regarding regulating the Radio Spectrum, Einstein discusses how The Radio Act of 1912 was put into place because there was an abundance of information filled with a diversity of voices on the airwaves. Because of this abundance, and lack of regulation, no one was getting heard, so the government began to regulate the Radio industry. The three major points in the Act established government control, based on what the government considered worthy and a priority of use, and individual communications were given priority over amateur communications.
There are many reasons as to why the Act was unsuccessful. It points to the fact that the government control over licenses within the spectrum allowed for a system of broadcasting where only a few large corporations dominated the source of the transmissions, which obviously was not serving the entire public interest. The Radio Act of 1927, and then the Communications Act of 1934, which declared the airwaves as a public resource and then reliance of advertising, provided the system of broadcasting we have today. As a public resource, the people using the airwaves had a requirement to provide the public with what they wanted to hear, and if they weren't serving the entirety of the public, the government had the right to shut it down.
This public space is as hard to define as diversity because programming became based on popularity, rather than on a diverse audience. The business was created by the regulating structure, but this in turn allowed for the serving of the public interest to fall on the back burner.