To simplify the calculations, I will only consider last year. How many astronauts were active last year? The number is not near 500 from the list. Some of them are dead. Some of them are behind a desk or doing public relation presentation. Some of them are retired or dead from natural events.
So, there are approximately 30 / 50 dead per year, from a population of 70 active astronauts, that is ~1%, or using a population of 30 flying astronauts we get a 2%.
http://en.wikipedia.org/wiki/NASA_Astronaut_Corps says "As of July 2011 the corps has 62 active astronauts, including 33 military officers, four medical doctors, and 15 with doctorates. The highest number of active astronauts at one time, was in 2000 when there were 149."
"only 339 candidates have been selected to date", but a couple of those candidates finished the program but did not go on with a career as an astronaut (one went into nuclear medicine instead).
"Twelve members of the Astronaut Corps were killed during spaceflight, Space Shuttle missions STS-51-L and STS-107. An additional seven were killed in training accidents. Sonny Carter died in a plane crash while traveling on NASA business."
So another way to reckon this is as 19 dead total from a total population of 339. 19/339 = 5.6% for the US program.
Assuming an average of 10 years, (1-p)10=(1-0.056) gives the probability of a person per year, which is 0.57%, or 580/100K/year.
I forgot to mention, your comment about the average number of years as an astronaut reminded me that I needed to use the right probability argument to get the statistics, rather than the coarse equation I used earlier. (HN ate my math: pow((1-p), 10) = (1-0.056) ) Thanks for pointing that out!
Let's suppose that the active period of an astronaut is 10 years. The number of astronaut selected in the last 10 years is approximately 70 (counting by hand from http://en.wikipedia.org/wiki/List_of_astronauts_by_year_of_s... ). Approximately only one half of them fly each year (~30 in 2009, ~25 in 2010 : http://en.wikipedia.org/wiki/List_of_human_spaceflights,_200... )
So, there are approximately 30 / 50 dead per year, from a population of 70 active astronauts, that is ~1%, or using a population of 30 flying astronauts we get a 2%.