I dont do a great job of tracking statistics but when you only sale a few homes a year its not to hard to remember. I am usually working with 10 or so clients in various stages of "house hunting" at a time so I will keep a page in my agenda with their hopes, dreams, finances and more importantly, things they do not like.

Dotloop, our contract software, keeps all my client information and old contracts so that i can pull them and review contract terms and personal details. I am always referring back to special stipulations that i have used in the past to address specific situations like low appraisals, leins, bonds or property issues. This is probably the best way I use previous data on current deals.