Usually the term 'statistics' makes me a little nervous since, despite what my transcript says, I didn't do so well in that graduate course. Luckily, library statistics are a little easier to deal with and don't involve charts and formulas.
Maintaining accurate and current statistics is very important for a number of reasons. They are required for annual reports, grant applications, and budget justifications. They can also help you keep your job when you can clearly show how many patrons are coming to programs, checking out materials, and using technology. It may appear to be good enough to tell an anecdote about how great the library program is, but the truth is numbers are important.
Keep up on your library stats by updating your records at least once a month. It is more impressive (and good for your sanity) if you have the numbers available when you need them. Keep track of visitors, circulation, program attendance, etc., in a spreadsheet. Data from database subscriptions may only be available going back a few years so don't rely on vendors to keep your stats for you.
Numbers can also help you evaluate your program by highlighting weak areas that you hadn't noticed before, such as low database usage or book circulation in a specific area. Using statistics to evaluate your program is an easy way to do a regular check-up on how your library is operating and gives you hard data to compare current activity to previous years.