Earlier quoted context omitted.
I did similar calculations, and found the institutions in charge give us very unreliable data. The term "corona case" is very, very, ambiguous and cannot the understood as such without a detailed explanation on how the counting was done. Thanks for sharing. I found the peek in all-case mortality also very interesting, because that way counting is much more unambiguous: dead is dead. They showed a clear diversion from…
Here is for Europe if you are interested. There are charts for excess morality by country, by age, and by year. https://www.euromomo.eu/ There is a very noticeable spike in the worst hit countries: Italy, Spain, France, Belgium, Netherlands and the UK. The cumulative excess deaths for all Europe in the last two months matches the COVID-19 reported deaths (around 100000).
Where's the noticeable spike for Ireland? Where's the spike for Portugal? Where's the spike for Luxembourg? Where's the data for the rest of Germany outside of Hesse and Berlin? Where's the spike for Austria? (And this is not a criticism of them, but they only track Western Europe by the looks of things.)
Don't know where Euromomo is getting its data from but I suggest to you that it's incomplete.
This NYT article[0] (other publications like The Economist[1] have arrived at similar numbers) show that the cumulative excess deaths for France, Netherlands, Switzerland, Spain, and England & Wales sometimes far exceeds reported Covid-19 deaths.
Of the countries you mention only Belgium is actually reporting accurately. (As is Sweden btw, a country you do not mention.) Note that both are smallish countries.
As of 14 hours ago Chris Giles (FT economics editor) tweeted[2] "A cautious estimate of the total number of UK excess deaths linked to coronavirus stands today at 42,700" (He updates this most days.) Worldometer[3] currently has the UK on 20,319 deaths. Quite a difference.
In fact, the numbers show that in Europe actual deaths are between 1.4 [Swiss] and 2.1 [British] times higher than the reported numbers for countries that are under-reporting.
Btw, you say that there are 100,000 deaths? EU 27 has 96,533 deaths as of this moment. EU+UK has 116,852 deaths as of this moment. And Europe in its entirety[4][5] has 122,568. (Am tracking these figures using a spreadsheet.)
Let's say that the adjustment we have to make is between 1.4 and 2.1 and let's ignore population size and pick 1.75 and then lower that to take into account that some countries are accurately reporting and let's err on the conservative side so let's choose 1.66… repeating as our adjustment rate, agreed? This gives us an estimated excess # of deaths for Europe of 204,280. Twice the figure you've given.
[0] https://www.nytimes.com/interactive/2020/04/21/world/coronav...
[1] https://www.economist.com/graphic-detail/2020/04/16/tracking...
[2] https://twitter.com/ChrisGiles_/status/1254105061745098752?s...
[3] https://www.worldometers.info/coronavirus/country/uk/
[4] https://en.wikipedia.org/wiki/Europe [5] https://www.reddit.com/r/europe/new/
(Europe is generally taken to extend from the Atlantic states of Ireland, Portugal, and Iceland in the West to the Ural and Caucasus Mountains in the east, from Scandinavia in the north to Italy and Greece in the south.)