When is or isn't the right time for a woman to report a rape?

When or under what conditions should a woman report being raped? Seeing that 1 in 6 women in her lifetime will either be raped or have a raped attempted upon her that is a lot of women and in 2008 there were 89,000 reported rapes (no numbers for 2009 and the US leads in number of rapes world wide, even beating Darfur). USA Today reported rape as being at an all time low largely do to DNA catching many rapist before they can victimize other women. I thought before engaging Fluther 80 to 89% of women raped would report it but I am getting an epiphany of sorts where many women don’t report it. Which makes me think under what circumstances do a woman just chuffs off the rape, shower up and move on keeping mum about being violated? If a 3rd party gets wind of it or discovered her after the rape as if she had to get help because of how badly battered she was and lacking clothes or having clothes badly ripped do she swear them to secrecy not to have to deal with it via law enforcement? What are conditions where she should not report?