Neil asks why we expect the new coronavirus to infect 80% of the populaton. According to Dr. Marty Makary, a medical professor at Johns Hopkins University, "Don’t believe the numbers when you see, even on our Johns Hopkins website, that 1,600 Americans have the virus, No, that means 1,600 got the test, tested positive. There are probably 25 to 50 people who have the virus for every one person who is confirmed.” He warned that the actual number of people walking around with the virus in the US could be “between 50,000 and half a million.” ( https://thehill.com/policy/healthcare/487562-johns-hopkins-professor-est...).
This is plausible when one considers what Government advice is currently in the UK: if you feel the symptoms, then self-isolate. Don't call the 111 helpline, just sit at home and take care of yourself. Of course, if you have more serious symptoms or other complications, then use the helpline.
But it you don't use the helpline, who will know you have (or had) covid-19? You will not be included in the statistics at all. The UK data must be understood from this perspective, just as in the US. To answer this question globally, you would have to look at what data are being collected in each country - including China.
HIFA profile: Chris Zielinski: As a Visiting Fellow in the Centre for Global Health, Chris leads the Partnerships in Health Information (Phi) programme at the University of Winchester. Formerly an NGO, Phi supports knowledge development and brokers healthcare information exchanges of all kinds. Chris has held senior positions in publishing and knowledge management with WHO in Brazzaville, Geneva, Cairo and New Delhi, with FAO in Rome, ILO in Geneva, and UNIDO in Vienna. Chris also spent three years in London as Chief Executive of the Authors Licensing and Collecting Society. He was the founder of the ExtraMED project (Third World biomedical journals on CD-ROM), and managed the Gates Foundation-supported Health Information Resource Centres project. He served on WHO’s Ethical Review Committee, and was an originator of the African Health Observatory. Chris has been a director of the World Association of Medical Editors, UK Copyright Licensing Agency, Educational Recording Agency, and International Association of Audiovisual Writers and Directors. He has served on the boards of several NGOs and ethics groupings (information and computer ethics and bioethics). UK-based, he is also building houses in Zambia. chris AT chriszielinski.com
His publications are at www.ResearchGate.net and https://winchester.academia.edu/ChrisZielinski/ and his blogs are http://ziggytheblue.wordrpress.com and https://www.tumblr.com/blog/ziggytheblue