Turning down a lot of candidates is not the same as finding good candidates. If you are turning down that many applicants, all it means is that your applicant pool is almost entirely bad candidates. That merely implies you are failing where it matters most, getting awesome candidates interested and excited about working for you.
I bet you could drive the P down even more. You could write worse job descriptions that get even more of the wrong people to apply. You could post the job listing on job boards like Monster or Dice, where there is a huge pool of un-hirable candidates who will apply to 20-30 jobs per day. I bet you could make it so bad you will have to hire someone to be the initial filter of candidates. Congratulations! You now have an HR department. They will arbitrarily filter candidates before the people actually competent to filter candidates get to see them, based entirely on buzzword bingo and 'number of years of experience'.
You are failing and you're proud of it!