The scene
The scene
Patricia had $5,000 of credit card debt at 21 percent interest. She saw an offer for a balance transfer to a new card. 0 percent interest for 15 months. She signed up.
The plan was clear. 15 months of zero interest meant she could focus all her monthly payment on the principal. $5,000 divided by 15 months was $334 a month. She would clear the debt by the end of the promo period, save all the interest, and end up free.
Month one, she paid $334. Month two, $334. Month three, a friend's birthday came up and she paid $200 that month. Month four, an unexpected car expense. Month five, she paid $334 again. Month six, holidays came up. By month nine, she was averaging about $200 a month instead of $334.
Month 15 arrived. The promo ended. She had paid $1,800 instead of $5,000. The remaining $3,200 immediately started accruing interest at 22 percent, on the new card. She had transferred the debt, not cleared it. The promotional period had given her the illusion of progress while life had absorbed most of the monthly payments she had planned.
She is not unusual. Studies of balance transfer customers have consistently found that a significant portion do not clear the full balance during the promotional window, ending up paying interest on the new card after the promo expires.
What your brain just did
What your brain just did
Our minds plan future tasks assuming our future selves will have more time, focus, and discipline than our current selves do. Patricia is not careless. Her brain ran the standard planning calculation that all our brains run when setting up a future financial goal, the way all our brains do when imagining a future version of ourselves who will execute the plan without the interruptions that actually exist. This behaviour has a name: Planning Fallacy.
What to do instead, in one move
What to do instead, in one move
The skill is to assume the future you is the same as the current you, with the same level of monthly discipline. If your current average monthly payment toward debt is $200, plan for $200, not $334. If $200 a month will not clear the balance during the promo period, the balance transfer is buying time, not freedom. The transfer can still make sense, but with realistic math, not aspirational math.
TL;DR
- Situation: You move debt to a 0 percent promotional card. You plan to clear it during the promo period.
- What your mind does: It estimates future monthly payments based on what you intend, not on what you have actually been doing (this is called Planning Fallacy, see below).
- Consequence: A significant portion of balance transfer customers do not clear the full balance during the promo, ending up with interest charges on the new card after the promo ends.
- What to do: Plan the monthly payment based on your actual average payments over the last six months, not on the optimistic amount needed to clear the balance.
What to do
- Before doing a balance transfer, look at your actual average monthly debt payment over the last six months. Use that number to estimate what you will pay during the promo period.
- If your actual average will not clear the balance during the promo, the transfer is still useful (zero interest is better than 21 percent), but it is not the final solution. Plan for what happens when the promo ends.
- Set up an automatic payment for the amount you decide. Automation beats intention. The brain that signed up for the transfer is not the same brain that will be there in month 12.
- Read the terms carefully. Some balance transfer cards charge a transfer fee (often 3 percent of the balance). Some have a "promotional payment first" rule that determines how payments are allocated. The fine print is where the actual deal is.
What not to do
- Do not plan the monthly payment based on what you would need to pay. Plan it based on what you actually have been paying.
- Do not assume the promo period is enough time. The promo period is the time given by the card. It is not the time your behaviour is likely to use.
- Do not transfer the balance and then make new charges on either the new card or the old one. The new charges defeat the purpose.
A balance transfer is not debt cleared. It is debt at zero interest for a fixed window. What happens in the window is the actual decision.
Want to understand why this happens?
Planning Fallacy is the brain's tendency to underestimate how long future tasks will take and overestimate how much progress we will make in a given period.
What the research found
Researchers have found the bias across virtually every domain studied. Construction projects, software development, household renovations, academic papers, exam preparation, weight loss, debt repayment. In each case, people who have actually done similar tasks before still underestimate how long the next one will take, by a consistent margin.
The mechanism is straightforward. When planning, the brain imagines the task being done by the version of ourselves that is currently planning. That version has focus, motivation, and clarity. The version that will actually do the task, day after day, has interruptions, lower energy, competing demands, and unforeseen events. The two versions are different people, and the planning version does not include the interruptions that the doing version will face.
What the research found
Kahneman and Tversky introduced the concept of Planning Fallacy in 1979 and followed it up in subsequent research. They documented that even experts predicting their own task durations consistently underestimate, by margins that can reach 50 to 100 percent of the actual time required.
A particularly striking study asked students to predict when they would complete their thesis. The students gave a most likely date, an optimistic date, and a pessimistic date. The actual completion times exceeded even the pessimistic estimates for most of the students. The same students, asked to estimate completion times for other people's theses, gave estimates that were closer to reality.
The fix is the same that researchers proposed for the original problem. Use what they called the "outside view". Instead of planning what you will do, look at what people doing the same kind of task have actually done in the past, including past versions of yourself. The outside view is less flattering than the inside view, and far more accurate.
For balance transfers specifically, the outside view is your actual monthly debt payment history. That number, projected forward, is what will determine whether the transfer clears the debt or just moves it.
"We plan for the version of ourselves who exists in our heads. We get the version of ourselves who actually shows up. The gap between the two is where projects expand." — Daniel Kahneman (paraphrased from Thinking, Fast and Slow, 2011, chapter on Planning Fallacy and the Outside View)
This is called Planning Fallacy. Kahneman and Tversky, Intuitive Prediction: Biases and Corrective Procedures (1979), expanded in Kahneman, Thinking, Fast and Slow (2011).
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