A week is the perfect measure of time.
A week is the most useful division of time. It is long enough to begin measuring contributions towards progress. To think of it as 2% of the year gives it the perfect amount of importance.
Imagine for this week, you go the gym or play a sport, save or plan towards your financial freedom, are available to friends and to family, you will have had a +2% yield toward the year (towards life!), all within one week.
Humans are terrible at grasping scale; "One week is 2% of the year" relativises how significant an amount of time a week can be.
What are more such phrases? I wonder.
I first read this phrasing at http://nat.org/.