This is a component of the ad hoc covid19 data project connected to the FUFF platform (fuff.org)
http://fuff.org/data/cr0.html
At the bottom of this page are tabs. Click there for individual countries.
please excuse the unformatted output. I will try to improve it. 
important: if you come back for updated versions, you have to refresh every single page!! sorry
This document is an attempt to make sense of the available data and tackle misunderstanding and misinterpretation that comes from unmoderated pure data 
- All the available data for corona is flawed (that applies for most data we work with)
- states report differently, states have individual problems aquiring the data, states define things differently, test differently, and maybe even manipulate
- what makes it even more difficult that there are phases which influence the reporting quality of a particular country, so that even the numbers of a single country can be inconsistent 
- example: we do know the number of 'officially confirmed cases', but we know that the number of sick people is bigger. but how much bigger?
- example: we do know that the number of actually infected people is much bigger because not everybody is tested and a good number has no or few symptoms. but how much bigger?
- example: we do know that the number of fatalities is bigger, in some countries much bigger than official numbers, because some contain only tested hospital cases, some only tested, some add other numbers and some don't even know what regional authorities include
- example: we do know that past cases that had not been counted are added at some date (all for that date) and from then on the data basis changes and is not comparable to what was reported before that date
- example: we do know that in most data that is collected in sources like ECDC and JHS, it is not the data 'as happened on that date' but data that 'was published on that date'. Means data for 1st of April is not the 1st of April data but incomplete cases that were counted on several, different days before by several local authorities and now published on 1st of April. 
(the sources do not claim else. Unfortunatley this misconception has been established in the public reception). 
- the only thing we know with the official data: we know that they are way off reality. but how far? and how different in different countries? (spoiler: a lot different and inconsistent in itself)
- this all makes clear: conclusions we draw from this official data, are flawed and have to be made very carefully!
- what I am trying to do here is make projections of 'real' data and compare them
- however here is the dilemma:
- any projections, as smart as they might appear, are more or less guesses. They do have a huge margin of error and are a similarly bad basis for any decisions, too.
- the projections here are simplified. They are supposed to be inspirations for others, to collaborate, or continue the development.
- I read often 'that prognosis was wrong'. Most of the times the 'prognosis' has not been understood.
example: it was asked to forecast the result of a dice throw with 5 numbers on it (1 2 3 4 5). Well, you say the average outcome is '3'.
But - in 80% of the cases it will be no 3. Let's say this time it was a 1. But was your prognosis really wrong? 
however... let's try:
the data            
is taken from ECDC, because they provide it in a format that is the smoothest to process. Read here how it is collected:
https://www.ecdc.europa.eu/en/covid-19/data-collection
However, all problems mentioned above apply. That is why I adjust some data for sources where I know abut the problem and know a fix.
This adjustment is made to have relative consistency of the data within a country. Only with this consistency you can calculate multiplication factors (a thing related to the famous R0) or make other timeline projections.
Example is the France data, where you had only hospital cases counted until April 2 and then other cases added. Or the UK, where all non hospital cases where added on one day. Similar effects for China.
Also you have flaws in the data collection like for ECDC data and Spain and US in the mid/second half of April (erratic high and low days and even minus numbers), so that I replace that data with sources that carry a similar total but distribution over days which make more sense. 
Unfortunately this is a lot of daily work, so I can only do this for a few cases.
You can track the adjustments in the data tabs
this document          
The country tabs are created automatically from a template. So all countries have the same charts and the same text explaining.
There are some specific comments about each country in the comments tab. They may be out of date sometimes.
There are so many tabs, you might have to scroll with the lower scroll bar to the right.
the excel file is send by email only
real cases           
- one idea is to estimate the number of real cases and/or infections by projecting them from the fatality rate
This has be done end of March by a study of Imperial college London. you can find this described below under 'real infections'
with a factor for undetected cases and a time variable for the time between infection and diagnosis you could conclude back on the number of cases (or future cases)
I have not implemented that for now
- onother idea I had is to estimate a minimum of real cases by norming the fatality rate to the one of Germany of a particular date.
the idea behind it:
Obviously, in Germany there had been a lot more testing. There had been a lot more less severe cases (without fatal outcome) and apparently a lot more diagnosed younger cases 
Though fatality rates in hot spots like North Italy or Madrid should indeed be higher. But also it had been reported that most of the fatalities in the crisis peak had not been counted as corona cases because the system was overwhelmed.
That could be at least partly offsetting effects helping us here.
(see further below for details and sources)
with the difference we adjust the case number of each country to the relation cases and fatalities have in Germany
Because of the fact that the situation in Germany is constantly changing, too I have now normed this comparison to the end of March value.
(Alternatively we could norm it to 1% instead which would be the value a few days before, what would lead to slightly higher projections, but the data basis is less solid for that)
- I have added a second projection with the same idea but probably a better base than the Germany numbers, as they are not perfect either. 
It is the rate of a collection of rather wealthy small countries that show two conspicious properties: a relatively high percentage of infections on the population vs. a very low CFR (case fatality rate) 
as of May10 they are Singapore, Kuwait, Bahrain, Qatar, Oman and United Arab Emirates
It is fair to assume they are testing a lot and come relatively close to identifying at least most cases, if not most infections. 
Of course that depends on their fatality data is relatively correct, and at least the inner consistency of the data is given.
I am thinking about adding a Qatar adjusted index as this is the maximum standout data at the moment. But it is so much above every other country that I am not sure whether we have some kind of artefact here. 
Also you have to consider that a lot of those countries do have a lot of guest workers which probably count in their cases (I do not know! I have not verified!) but probably does not count in their population number (I do not know! I have not verified!)
As long both is the same in fatality and case number it will not hurt the projection though, but the selection criteria.
a thumb rule might be: for countries with an overwhelmed but basically good health system the SWT projection might be too high, because the real CFR is higher in that case (ex. the Italy crisis period)
for countries with no good health system and no testing in place (example the Ecuador case), a projection is probably still far too low.
for countries with a good health system and no severe crisis, SWT projection is probably quite close, although the true number of infections might still be higher.
discarded:
- there was a second way to 'norm' numbers to the German scenario:
comparing it with an minimum expectation value that is derived from the following mid-march stat:
(yes, we need a better source for this statistics than this image)
We would assume that Spain and Italy should have an 80:20 distribution as well - if just enough people were tested
Or the other way round: we assume that a minimum amount of round about +150% cases are diagnosed in Germany (and in younger people alone) that are not even tested in Italy or Spain  
(the ~ 50:50 distribution of Italy and Spain find itself in a ~20:20 distribution in Germany, and then you have another 60% (which is 150% more that 40%))
And this even could be higher - you would guess there was also a higher number of tested older people. But we don't know so we go for the minimum.
So the factor for 'minimum real cases' derived from this for Italy and Spain would be at least 2.5. This is a careful low value.
->  Don't forget that the Germany number of 'confirmed cases' is probably still far away from the real number of cases (symptomitic) and infections (symptomatic and asymptomatic) themselves!
However I discarded this projection, because it isn't flexible for different countries because I do not have the data, so the projections are not valid for countries who do test like Germany. 
Also the contexts of testing have changed over time in every country, so that this data is indispensable to make this projection valid
not implemented:
another way of projection of real cases (or maybe infections or a value in between) is to take a countries testing of health care personnel in relation to the ordinary patients.
if it is a projection of infections or real cases (or a value in between) depends on the actual scenario of testingof the healthcare workers
in wikipedia I found the following snippet for Spain:
'According to Fernando Simón, only 8.8% of diagnosed healthcare workers require hospitalization, in contrast to 40% of other cases of the disease. '
the idea now would be that this gap is caused at large part by the gap in testing between the two groups and that the number 
from this relation and the number of official cases we could project a number that is likely somewhere closer to the number of real cases/infections
I have neither researched this for other countries nor implemented it for Spain yet.
In the end you will have a bunch of projections that should give you at least an interval of cases that is closer to reality than official numbers.
Another way is combining several ideas and building an average index value. But be careful, you still have to consider an interval around it as it is still the same projections and it only tricks you into simplifying without justification.  
Very important is also that because of the difference in data between countries projections that might be to high here might be too low there.
infections          
Distinguishing between 'real cases' and 'infectons' is a bit odd, there is no clear border. It historically stems from the beginning of testing where usually only symptomatic cases were tested. Consider that this monitor already exists since early March. So somethings may need a redesign.
Intuitively 'cases' comprise people who develop symptoms and so more or less suffer from desaese.
Meanwhile projection for infections try to estimate how many have been infected, including also the ones who show no symptoms at all. 
- a simple idea is to use an assumed value for undetected infections (no or low symptoms) and multiply the number of (projected) cases with that
downside: this factor is varying a lot between countries and withi country data, depending on the how much the country is testing and how much testing was improved. so the accuracy might bounce a lot. 
I tried to account for that by using the case projections described above, using a little different multiplicators to compensate for assumed method difference
- one idea is to estimate the number of real cases and/or infections by projecting them from the fatality rate
this has be done just recently by a study of Imperial college and I will use the numbers for comparison here
link to the study: https://www.imperial.ac.uk/media/imperial-college/medicine/sph/ide/gida-fellowships/Imperial-College-COVID19-Europe-estimates-and-NPI-impact-30-03-2020.pdf
downsides: the fatality numbers are higly flawed as well. I will go to that in detail further below
I have applied a projection that is derived from those estimations from the study. See the charts on the country sheets.
This method is only applied to some of them, the ones mentioned in the study.
For the other countries a lower quality secondary projection could be made, however. By using the resulting factor (projection to cases) from the countries present in the study and applying it to the non present countries/regions.
not implemented:
Another way of projection of real cases (or maybe infections or a value in between) is to take a countries testing of health care personnel in relation to the ordinary patients.
If it is a projection of infections or real cases (or a value in between) depends on the actual scenario of testingof the healthcare workers
(see explanation above for real cases)
fatalities            
critical cases and fatalities have seen huge spikes in hot spots of the crisis.
communities have started to compare the numbers with the annual averages and found that a huge share (50-90% in the example cases below) of the excess numbers are unexplained. 
meanwhile news outlets like NYT, Economist, and FT have build special monitors for so-called 'excess data', that appears to be the most precise detector for the real number of Covid19 fatalities. 
(from there it might be even a good way back to estimate the true course of the infection curve once the studies on mortality settle more on similar values)
(At the moment they still have erratic variances so that the old estimates from China appear still the most plausible, a minimum of 0.5% in managed situations, can rise up to 5% in crisis hot spots)
new ressources from April:
monitoring:
NYT
https://www.nytimes.com/interactive/2020/04/21/world/coronavirus-missing-deaths.html
Economist
https://www.economist.com/graphic-detail/2020/04/16/tracking-covid-19-excess-deaths-across-countries
FT
https://www.ft.com/coronavirus-latest
older ressources from March:
see
https://elpais.com/sociedad/2020-03-27/el-coronavirus-causa-mas-muertes-de-las-detectadas.html
see also this snippet from wikipedia for Spain
https://en.wikipedia.org/wiki/2020_Spain_coronavirus_quarantine#Underreporting
see Italian sources
a US study:
However, trying to add more of the undetected cases to the official data causes another problem of inconsistency in the timelines. This has already been adressed at other places in this document.
Here only fatalities in hospitals had been counted. April 2 they appended data from other sources, although apparently not in a clean daily rhythm, which lead to artefacts on the timeline.
immunity          
So the 'real' numbers of infections are higher. Are places closer to collective ('herd') immunity?
This can not be generally answered. The projections are made for countries which in most of the cases have intervented after having regional crisis clusters vs. other clusters with relatively low infection rates.
So at this point the answer that countrywide projections deliver are insufficient. 
I recommend to play a little with the experimentation panel to understand the mechanics of clustered scenarios.
http://fuff.org/data/cr0.html