Say you live to about 80. About how many weeks of life is that, total?
A week feels short. A life feels long. But a life is just weeks, stacked up. Live to 80, and you get about 4,000 of them.
Sources
Oliver Burkeman, Four Thousand Weeks (2021)
The Decision Lab
American Psychological Association, “Multitasking: Switching costs”
Cal Newport, Deep Work (2016)
Valdez et al., Circadian Rhythms in Attention, PMC/NIH
Mark, G., Gonzalez, V. M., & Harris, J. (2005). "No Task Left Behind? Examining the Nature of Fragmented Work." Proceedings of CHI 2005, 321-330. https://ics.uci.edu/~gmark/CHI2005.pdf (measured: 25 min 26 sec to resume interrupted work; 2.26 intervening tasks; ~11 min per working sphere)
Rubinstein, J. S., Meyer, D. E., & Evans, J. E. (2001). "Executive Control of Cognitive Processes in Task Switching." Journal of Experimental Psychology: Human Perception and Performance, 27(4), 763-797. (goal shifting + rule activation)
American Psychological Association (20 March 2006). "Multitasking: Switching costs." https://www.apa.org/topics/research/multitasking (source of the quoted sentence and of Meyer's 40% estimate)
American Psychological Association, Speaking of Psychology ep. 225 (February 2023). "Why our attention spans are shrinking, with Gloria Mark, PhD." https://www.apa.org/news/podcasts/speaking-of-psychology/attention-spans (2.5 min in 2004; 75 s around 2012; ~47 s in recent years)
Valdez, P. (2019). "Circadian Rhythms in Attention." Yale Journal of Biology and Medicine, 92(1), 81-92. https://pmc.ncbi.nlm.nih.gov/articles/PMC6430172/ (single author - the current source list says "Valdez et al.", which is wrong)
Newport, C. (2013). "Deep Habits: The Importance of Planning Every Minute of Your Work Day." https://calnewport.com/deep-habits-the-importance-of-planning-every-minute-of-your-work-day/ (the 40-hour vs 60-hour estimate)
Foundation for Teaching Economics. "Lesson 1: Opportunity Cost." https://www.fte.org/teachers/teacher-resources/lesson-plans/edsulessons/lesson-1-opportunity-cost/ (source of "Whenever a choice is made, something is given up.")
Caceres-Santamaria, A. (29 January 2020). "Real-Life Examples of Opportunity Cost." Federal Reserve Bank of St. Louis, Open Vault. https://www.stlouisfed.org/open-vault/2020/january/real-life-examples-opportunity-cost
Kahneman, D., & Tversky, A. (1979). "Intuitive Prediction: Biases and Corrective Procedures." TIMS Studies in Management Science, 12, 313-327. (coins "planning fallacy"; the outside view)
Lovallo, D., & Kahneman, D. (July 2003). "Delusions of Success: How Optimism Undermines Executives' Decisions." Harvard Business Review.
Covey, S. R. (1989). The 7 Habits of Highly Effective People, Habit 3. ("Quadrant II is the heart of effective personal management.")
Parkinson, C. N. (19 November 1955). "Parkinson's Law." The Economist.
Read end to end and corrected: August 10, 2026. Numbers checked: August 10, 2026.