Interesting numbers. First, the average total permanent resident population in Singapore is about 500,000 (488,700 IN 2020, 521,000 IN 2019). So, if you look at PR's granted, it works out to be a pretty solid 6 percent of the total PR population each year.
Second, in comparing PR's granted to citizenships granted, it's pretty much that the new citizens count is about 70 percent of the new PR count year after year, so, perhaps the gahmen is really making a concerted effort to find citizenship material (ie - don't apply if you're not going to be a citizen).
So... as a rough rule, 6 percent is added to the PR population each year, while 4 percent of the PR population becomes citizens.