Roughly how many Christian priests, and how many 'rotten apples' are there? The credibility of Christianity has been severely damaged by a few Christian Priests being found guilty of molesting minors. I would like to quantify just how small a minority this is. So how many Priests/ministers are there in the world, and how many have been found guilty of pedophilia?
In a way, it would be unfair to single out the Catholic Church,given that similar problems have surfaced among Protestant clergy and Jewish rabbis. However, the Catholic Church has received most reporting on the issue of child sex abuse.  We will never know the total number of priests who have offended as the preference of most denominations, not only the Catholic Church, has always been to deny the problem if possible and, if this is not possible, to deal with it internally. It has long been the practice to cover up offences and move offending clergy to other parishes, which may be located in other countries if there is a risk of police intervention. As long ago as the early 1870s, Mother Superior Saint Mary Mackillop was excommunicated by the Church, not because she personally exposed a paedophiliac priest operating in Adelaide, Australia, but because one of her nuns simply reported the priest to his bishop, and the priest had to be relocated to Ireland. 

In many cases, a priest will have died before any of his victims has plucked up the courage to report past abuse. In many more cases, victims suicide or simply choose not to relive the past trauma by going to the police. Some have received small amounts of compensation and some counselling, on the strict understanding of confidentiality. Thus, we can only look at the numbers that have been reported and hope there were not too many more.

I can best report on the problem as we find it in Australia, as a representative sample that may apply in other jurisdictions. Official figures say there were 3085 priests (1948 diocesan priests and 1137 in religious orders) and 930 religious brothers in Australia in 2009; 495 diocesian priests - nearly a quarter - are retired and if they are no longer active in the Church they are  of little interest in this type of comparison.  

An incomplete list published by Broken Rites, reports that over 200 Catholic priests and brothers were tried and convicted in Australia since 1993 for criminal offences against children. A large number of priests also faced civil actions taken out by victims who were unwilling to relive the terrible events in criminal trials. Victims run into the thousands.

A newspaper article published in 12 November 2012, says a psychologist who was employed by the Brothers of St John of God claims that more than 70 per cent of the Brothers of St John of God [in Australia] are suspected child abusers. I personally note that suspicion does not mean guilt is proven.

The unstated question is whether these figures are significantly worse than those in the population at large.  I have seen Catholic suggestions that around 5 per cent of men are paedophiles, and other more specific suggestions of a similar percentage among male leaders in groups such as the Boy Scouts.