According to the 2007 FBI Crime stats

1. Number: In 2007, 17.5 million property crimes occurred.
2. Frequency: A burglary occurs every 14 seconds in the States. Truly frightening when one thinks about it.
3. Time of day: the vast majority of burglaries take place in the day: between 6am and 6pm. personally talking, my home has been broken into twice (a long time ago - before I got an alarm system), and both times happened during noon.
4. Entry points: The burglar enters through the main entrance to the house, normally the front door, in more than a third of robberies. This was the argument for my break-ins as well.
5. Crime trends: traditionally talking, when the economy is not doing well, property crime and robbery have risen.
6. Biggest factor, and most interesting: houses with monitored security systems are three times less sure to get broken into or robbed than houses without this kind of a system. Thieves are not stupid and can say when it is much more likely they are going to be caught. By simply raising the bar of difficulty, you're pushing the potential thief to pick a different place rather than yours.