If you'd like to know how many projects were lost (in a given period) you can use your Project List.

Since we're searching for Lost projects, they'll already be archived - make sure to check off Include Archived Projects, to the left of your screen below your Project Filters.

If you click on the 'Lost' flag at the top of your Project List you'll just see your Lost projects, and the total amount of lost projects in the time range (if you're using one).

You can filter by date, by sales lead, etc on the left, and then use the Custom Columns (Learn More) to find out the totals for your Lost projects.