Why It took radio broadcasters 38 years to reach an audience of 50 million television 13 years and the Internet just four?

This question does not compare the same things. First of all, when radio broadcasting started, radio receivers were prohibitively expensive compared to disposable family income for most people. PLUS you needed to pay a license fee to even listen to your own radio. RadiOS got cheaper over time but not to the extent that we have seen digital equipment drop in price over the past 30 odd years. When television broadcasting started, disposable income of the average family was a lot more than when radio started so more people could actually afford a TV. When the internet started the first adopters of it ALREADY HAD a computer. All they needed was a browser and an internet connection. I had a PC in my house 10 years before the internet was easily available to me. So this question does not really compare equal things at all. Adoption of new technologies has increased over the years since say, the telephone was brought out. ALSO the question is looking a a simple number. There are MANY MORE people today than when radio was introduced. A better metric would be percentage of the population and not a static number.