The RAE and successors used a number of indicators together to come to the final decision on the classification of the Department, or, these days, the individual before being aggregated into a departmental profile. In the early versions (this would be about 1985) it was a purely paper exercise where research income and type and number of publications were used and this was grossly unfair. In later versions each academic was asked to choose three publications during the assessment period and to say why they were significant. Departments were able to choose whether or not a particular academic was put into the process. If they weren't put in then there would be no research money attributed to them. Such academics had then to accept that their role in the Department would be in teaching and administration, releasing the time of research active staff. Unbelievably prior to the introduction of RAE this had never happened. Many such staff took early retirement. My own Department carefully allocated teaching on an equal basis irrespective of whether they did research or not. This meant some of us worked all hours and weekends. My second daughter Kathy told me recently told me that summer was when her father didn't work every weekend (and while watching TV). So the whole process should be seen as a way of Departments coming to terms with organising themselves in a way which allowed them to enter an upper grouping of Departments that receive a significant amount of money for research and, as a result, could employ more staff and have lighter teaching loads and a well equipped laboratory.
But the central subject committees eventually looked at a profile of data on each academic. Someone would agree to look at the three paper submitted and the commentary for each academic. They also looked at indicators of esteem - plenary lecture at world congresses etc. They now also look at overall management - the consistent development of research themes over many years.
The statistics you quote sound pretty dire and, of course, the purpose of the exercise is to expose such features for debate. It rather sound as if you have a lot of academics who might not be considered in the UK assessment. I suspect we are more of a debating academic society and a less hierarchical society that Italy. As a result the process may have different consequences.
Certainly they was a great deal of discussion of the way in which academics in different subjects contribute. In the English Department an academic I highly respected produced nothing in print until his early 30's when he published the definitive book on his subject - leading to one of the mani Chairs in English in the country. There is the problem of the academic who is going to produce the great book and persuades the University to fund his trips to Venice or somewhere equally pleasant each spring but it never appears. In Social Sciences, the PhD is usually the first book and can take years. The criteria published by the Higher Education Funding Council on the web discusses the criteria for groups of subjects and then these are interpretations within the panels in each subject. When I met up with people in Humanities over such issues, I had to keep reminding them that it was a peer revue system - ultimately by various roots the accessment was going to be made by people they knew only too well. They should get out more and demonstate their abilities - write short papers, go to conferences etc. They would often say that they would if I gave the Department more money but I reminded them that the logic of assessment means it works the other way around.I point out that at least some of the figures you present for Italian Universities are not dissimilar to those of UK universities. I imagine, by the nature of things, you would find much the same if you looked at all US universities. All it tells you is that top flight research is concentrated in a proportion only of a nation's universities, while the rest prepare students for professional work etc, and their academics are equally hardworking and of value to society. In other words, you are producing figures that are worthless unless interpreted in terms of the structure of your higher education system and how it may differ from, say, the UK system.