This question is difficult to answer because it is vaguely posed. If you set some clear age of old age, say, up to 100 years, then now more people are living out than before. But this is different in different countries, and it is a changing value. They live longer, because now the mortality rate is completely different from what it used to be, but here's what percentage survive - I find it difficult to say, because there are few hundred-year-old people. If you take the number of centenarians, for example, in 2015, then you should know how many children were born in 1915. This will be the percentage: the ratio of the number before 2015 in relation to the number of births in 1915. But this is all not very definite, because it is necessary to set age limits.
But a very small percentage live to a ripe old age. For example, even if we consider those who live to be 80 years old. Those who are now living to 80 years old are the generation of the 30s. They are now in their 80s or early 80s. They went through wars, events that have different impacts on different generations. Therefore, a specific percentage cannot be named. It all depends on what events happened during the life of people who lived to old age. If, for example, this is a generation that met the war and they have already participated in the war, then the percentage of survivors, of course, is less. If people were born after the war and did not fight, then the percentage of survivors will be higher, regardless of anything else. In addition, medicine is improving. Therefore, if people were born after, for example, the same antibiotics were invented, then the percentage there will be greater. Therefore, it is simply impossible to say what percentage survives. Demographers use an indicator of life expectancy, but this is not the same indicator. It is simply an indicator of how old those born this year can live if the mortality rate at all ages is the same as this year, throughout their life. But this does not happen, because mortality is now constantly decreasing and changing.
Well, if you just think about it very little. I would like to know exactly where, in which country at least. In general, it is very difficult to say all over the world. But I think you had Russia, therefore, taking into account: alcoholism, low level of health care , leading indicators for HIV infection, murders, car accidents and other bunch of troubles, I think ... 30 percent offhand. Maybe more, 10 percent.