Bitcoin Q&A: What is difficulty targeting?

How does difficulty targeting work? What determines the desired pattern? Should difficulty re-targeting still happen every 2016 blocks? Could difficulty changes (and hence profitability changes) make all miners drop out?

These questions are from the MOOC 7.2 and 9.2 sessions, which took place on February 26th 2017 and February 23rd 2018 respectively. Andreas is a teaching fellow with the University of Nicosia. The first course in their Master of Science in Digital Currency degree, DFIN-511: Introduction to Digital Currencies, is offered for free as an open enrollment MOOC course to anyone interested in learning about the fundamental principles.

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This audio content, description, and imagery has been extracted from the original YouTube video https://youtu.be/h429LCTRmQw and is licensed under Creative Commons [CC BY http://bit.ly/yt-cc-by]. Credit to Andreas M. Antonopoulos https://twitter.com/aantonop