







People systematically underestimate exponential growth. This article illustrates this phenomenon, its implications, and some potential interventions in the context of saving for retirement, where savings grow exponentially over long periods of time. Experiment 1 shows that a majority of participants expect savings over 40 years to grow linearly rather than exponentially, leading them to grossly underestimate their account balance at retirement. Experiment 2 demonstrates that this misunderstanding leads to underestimates of the cost of waiting to save, which makes putting off saving more attractive than it should be. Finally, Experiments 3–5 show that highlighting the exponential growth of savings motivates both college students and employees to save more for retirement. Making clear to employees the exponential growth of savings before they make crucial decisions about how much to save may be a simple and effective means of increasing retirement savings.
Temporal Reframing and Participation in a Savings Program: A Field Experiment
This study explores whether framing savings in more or less granular formats can increase sign-ups for a recurring deposit program in a FinTech environment. , A growing number of American workers are now freelancers and thus, responsible for their own retirement savings, yet they face psychological hurdles that hamper them from saving enough money for the long term. Although prior theory-derived interventions have been successful in addressing some of these obstacles, encouraging participation in saving programs is a challenging endeavor for policy makers and consumers alike. In a field setting, we test whether framing savings in more or less granular formats (for example, saving daily versus monthly) can encourage continued saving behavior through increasing the take up of a recurring deposit program. Among thousands of new users of a financial technology app, we find that framing deposits in daily amounts as opposed to monthly amounts quadruples the number of consumers who enroll. Furthermore, framing deposits in more granular terms reduced the participation gap between lower- and higher-income consumers: three times as many consumers in the highest rather than lowest income bracket participated in the program when it was framed as a $150 monthly deposit, but this difference in participation was eliminated when deposits were framed as $5 per day.

Knowing When to Spend: Unintended Financial Consequences of Earmarking to Encourage Savings
Maintaining savings is an important financial goal. Yet there are times when savings should be spent, such as when people face unavoidable costs, and spending their savings allows them to avoid high interest rate debt. Existing behavioral research has focused on consumer decisions between savings and discretionary spending and has proposed interventions to promote savings in these contexts. However, when spending is not discretionary, such interventions could risk exacerbating a pattern found in economic research in which people borrow high interest rate debt while maintaining savings that earn low levels of interest. To examine how mental accounting interacts with considerations of personal responsibility and guilt to contribute to this pattern, this article explores whether people spend their savings when they need money most: during emergencies. Six studies reveal that people's tendency to preserve savings by borrowing from a high interest rate credit option varies as a function of the savings’ intended use. Paradoxically, people are most likely to turn to high interest rate credit with the belief that doing so is the responsible option.

Save More Today or Tomorrow: The Role of Urgency in Precommitment Design
To encourage farsighted behaviors, previous research suggests that marketers should invite consumers to precommit to adopting these behaviors “later.” However, the authors propose that people will draw different inferences from different types of precommitment offers, and that these inferences can help explain when precommitment is (and is not) effective at increasing adoption of farsighted behaviors. Specifically, the authors theorize that simultaneously offering consumers the opportunity to adopt a farsighted behavior now or later (i.e., offering “simultaneous precommitment”) may signal that the behavior is not urgently recommended; however, offering consumers the opportunity to adopt that behavior immediately and then, only if they decline, inviting them to adopt it later (i.e., offering “sequential precommitment”) may signal just the opposite. In a multisite field experiment (N = 5,196), the authors find that simultaneously giving consumers the chance to increase their savings now or later reduced retirement savings. Two preregistered lab studies (N = 5,080) show that simultaneous precommitment leads people to infer that taking action is not urgently recommended, and such inferences predict less adoption of recommended behaviors. Importantly, offering sequential precommitment increases inferred urgency, predicting greater adoption. Together, this research advances knowledge about the limits and potential of precommitment.

Balancing Savings and Debt: Findings from an Online Experiment
Many consumers have savings and debt at the same time, and so are faced with a trade-off: how much debt to pay down versus how much savings to retain. This brie
Earmarking and Partitioning: Increasing Saving by Low-Income Households
This research examines the effects of earmarking money on savings by low-income consumers. In particular, the authors test two interventions that are designed to enhance the effects of earmarking: (1) using a visual reminder of the savings goal and (2) dividing the earmarked money into two parts. Consistent with prior research suggesting that partitioning increases self-control, people save more when earmarked money is partitioned into two accounts than when it is pooled into one account. In addition, the presence of the visual reminder increases the savings rate. The authors conclude with implications for consumer welfare and directions for further research.

When Motivation is against Debtors' Best Interest: The Illusion of Goal Progress in Credit Card Debt Repayment
The authors explore the illusion of goal progress by consumers who own multiple credit cards and pay off their debt balances to facilitate the achievement of their subgoal rather than the superordinate goal of being debt-free. The first experiment shows that debtors use their savings toward the credit card debt they can pay off entirely or substantially, even if it is associated with the smallest balance and the lowest annual percentage rate rather than toward the debt with the highest annual percentage rate. The second experiment reveals that when the income available to pay down the debt is in the form of effortless money (i.e., windfall or reward money) as opposed to hard-earned savings, the tendency to allocate money toward the smallest credit card debt is exacerbated. However, people tend to pay their debt more rationally when the number of debt accounts increases. Finally, the third experiment shows that credit card debt repayment decisions depend on the nature of the debt (hedonic vs. utilitarian) and the timing of consumption benefits (past vs. future). The article concludes with a discussion of managerial and public policy implications.

Exponential Growth Bias and Household Finance
ABSTRACT Exponential growth bias is the pervasive tendency to linearize exponential functions when assessing them intuitively. We show that exponential growth bias can explain two stylized facts in household finance: the tendency to underestimate an interest rate given other loan terms, and the tendency to underestimate a future value given other investment terms. Bias matters empirically: More‐biased households borrow more, save less, favor shorter maturities, and use and benefit more from financial advice, conditional on a rich set of household characteristics. There is little evidence that our measure of exponential growth bias merely proxies for broader financial sophistication.

Identifying heterogeneity using recursive partitioning: evidence from SMS nudges encouraging voluntary retirement savings in Mexico
Abstract Individuals regularly struggle to save for retirement. Using a large-scale field experiment (N=97,149) in Mexico, we test the effectiveness of several behavioral interventions relative to existing policy and each other geared toward improving voluntary retirement savings contributions. We find that an intervention framing savings as a way to secure one’s family future significantly improves contribution rates. We leverage recursive partitioning techniques and identify that the overall positive treatment effect masks subpopulations where the treatment is even more effective and other groups where the treatment has a significant negative effect, decreasing contribution rates. Accounting for this variation is significant for theoretical and policy development as well as firm profitability. Our work also provides a methodological framework for how to better design, scale, and deploy behavioral interventions to maximize their effectiveness.

Savers and Borrowers: Strategies of Personal Financial Management
Saving and borrowing are traditionally and stereotypically thought of as opposites, with different motivations and consequences. Through a questionnaire survey of economic position, practices, and attitudes, the present paper examined the relation between saving and borrowing among British respondents. While saving and borrowing were found to be determined by different economic, social, and psychological factors, they did not describe mutually exclusive strategies of financial management. Saving regularly could also be distinguished from having savings. In all, six strategies were identified (combining saving or not saving, borrowing or not borrowing, and having or not having savings). Each combination was found to have specific discriminating characteristics. Savers and borrowers were found to have different psychological motivations, seeing debt either as a failure or as a normal part of everyday life. Many people retained savings or carried on saving at the same time as having debts: they were found to feel more in control and optimistic about their financial position than those who had debts but no savings. A further group had neither debts nor savings: they adopted an inflexible approach to financial management. Each group of people with different financial management strategies was illustrated by a case study.

Behavioral Impediments to Valuing Annuities: Complexity and Choice Bracketing
Abstract This paper examines two behavioral factors that diminish people's ability to value a lifetime income stream or annuity, drawing on a randomized experiment with about 4,000 adults in a U.S. nationally representative sample. We find that increasing the complexity of the annuity choice reduces respondents' ability to value the annuity, measured by the difference between the sell and buy values they assign to the annuity. When we limit narrow choice bracketing by inducing people to think first about how quickly or slowly to spend down assets in retirement, their ability to value an annuity increases.

What Would You Do with $500? Spending Responses to Gains, Losses, News, and Loans
Abstract We use survey questions about spending in hypothetical scenarios to investigate features of propensities to consume that are useful for distinguishing between consumption theories. We find that (1) responses to unanticipated gains are vastly heterogeneous (either zero or substantially positive); (2) responses increase in the size of the gain, driven by the extensive margin of spending adjustments; (3) responses to losses are much larger and more widespread than responses to gains; and (4) even those with large responses to gains do not respond to news about future gains. These four findings suggest that limited access to disposable resources, and frictions in adjusting consumption, are important determinants of consumption behaviour. We also find that (5) households do not respond to the offer of a one-year interest-free loan, suggesting that this is not a consequence of short-term credit constraints; and (6) people do cut spending in response to news about future losses, suggesting that neither is this a consequence of myopia. A calibrated precautionary savings model with utility costs of changing consumption, and a sufficient fraction of low-wealth households, can account for these features of propensities to consume on both the extensive and intensive margins.

Misperception of Exponential Growth: Are People Aware of Their Errors?
Previous research shows that individuals make systematic errors when judging exponential growth, which has harmful effects for their financial well-being. This study analyzes how far individuals are aware of their errors and how these errors are shaped by arithmetic and conceptual problems. Whereas arithmetic problems could be overcome using computational assistance like a pocket calculator, this is not the case for conceptual problems, a term we use to subsume other error drivers like a general misunderstanding of exponential growth or overwhelming task complexity. In an incentivized experiment, we find that participants strongly overestimate the accuracy of their intuitive judgment. At the same time, their willingness to pay for arithmetic assistance is too high on average, often much above the actual benefits a calculator provides. Using a multitier system of task complexity we can show that the willingness to pay for arithmetic assistance is hardly related to its benefits, indicating that participants do not really understand how the interplay of arithmetic and conceptual problems shape their errors in exponential growth tasks. Our findings are relevant for policymaking and financial advisory practice and can help to design effective approaches to mitigate the detrimental effects of misperceived exponential growth.

Getting to the Top of Mind: How Reminders Increase Saving
We provide evidence from field experiments with three different banks that reminder messages increase commitment attainment for clients who recently opened commitment savings accounts. Messages that mention both savings goals and financial incentives are particularly effective, whereas other content variations such as gain versus loss framing do not have significantly different effects. Nor do we find evidence that receiving additional late reminders has an additive effect. These empirical results do not map neatly into existing models, so we provide a simple model where limited attention to exceptional expenses can generate undersaving that is in turn mitigated by reminders. Data, as supplemental material, are available at http://dx.doi.org/10.1287/mnsc.2015.2296 . This paper was accepted by Teck-Hua Ho, behavioral economics.

5: Behavioural biases in personal finance
Behavioural economics merges psychology and economics to explore systematic deviations in financial decision-making from traditional economic models. This chapter examines key biases such as mental accounting, present bias, planning fallacy, and misunderstanding of risk, which influence spending, saving, investing, and insuring decisions. Demonstrating the interplay of cognitive biases and heuristics highlights why individuals make suboptimal choices despite financial literacy and resource capacity. Strategies like goal-setting, commitment devices, and education interventions are evaluated, focusing on their limitations and potential for addressing these biases. The chapter concludes by emphasising the need for systemic changes, such as policy-level interventions and financial regulation, to complement behavioural interventions and address structural barriers to better financial decisions. Future research directions are suggested, including tailoring interventions, exploring technology's role, and integrating systemic solutions to support sustainable financial well-being.
The Effect of Credit on Spending Decisions: The Role of the Credit Limit and Credibility
The objective of the present research is to study consumer decisions to utilize a line of credit. The life-cycle hypothesis from economics argues that consumers should intertemporally reallocate their incomes over their life stream to maximize lifetime utility. One form of intertemporal allocation is to use past income (in the form of savings) in the future. A second form is the use of future income in the present. This can only be done if consumers have access to a temporary pool of money that they can draw from and replenish in the future—a function performed by consumer credit. However, our research reinforces prior findings that consumers are unable to correctly value their future incomes, and that they lack the cognitive capability to solve the intertemporal optimization problem required by the life-cycle hypothesis. Instead, we argue that consumers use information such as the credit limit as a signal of their future earnings potential. Specifically, if consumers have access to large amounts of credit, they are likely to infer that their lifetime income will be high and hence their willingness to use credit (and their spending) will also be high. Conversely, consumers who are granted lower amounts of credit are likely to infer that their lifetime income will be low and hence their spending will be lower. However, based on research in the area of consumer skepticism and inference making, we also argue for a moderating role of the credibility associated with the credit limit. Specifically, we argue that the above effect of credit availability would be particularly strong for consumers who believe that the credit limit credibly signals their future earnings potential (i.e., a naïve consumer who has limited experience with consumer credit). However, as consumers gain experience with credit, they start discounting credit availability as a predictor of their future and start questioning the validity of the process used to set the credit limit. Hence, with experience the effect of credit limit on the willingness to use credit should be attenuated. We test these predictions in five separate studies. In the first experimental study, we manipulate credit limit and credibility and pose subjects with a hypothetical purchase opportunity. Consistent with our prediction, credit limit impacted the propensity to spend, but only when the credibility was high. In the second experimental study, we replicate these findings even when subjects were given information about their expected future salaries, and also show that the credit limit influences their expectation of future earnings potential. In the third study, we show that the mere availability (and increase) of current liquidity cannot explain our findings. In the fourth study, we conduct a survey of consumers in which we measure a number of demographic characteristics and also ask them for their propensity to spend in a given purchase situation. In the fifth study we use the Survey of Consumer Finances (SCF) dataset, a triennial survey of U.S. families that is designed to provide detailed information on the use of financial services, spending behaviors, and selected demographic characteristics. Results from both studies 4 and 5 provide further support for our proposed framework—credit limits influence spending to a greater extent for consumers with lower credibility: younger consumers and less-educated consumers. Across all studies we achieved triangulation by using a variety of approaches (surveys and experiments), subjects types (young students and older consumers), nature of predictor variables (manipulated and measured), dependent measures (purchase likelihood, credit card balance, new charges), and methods of analysis (ANOVA and regression), and consistently found that increasing credit limits on a credit card increases spending, especially when the credibility of the limit is high. This paper joins a growing body of literature in marketing and behavioral decision theory that goes beyond the traditional domains of inquiry (e.g., product choice, effects of marketing mix variables) and focuses on consumer decisions relating to the appropriate use of income to finance consumption. Our framework differs from prior research on the effect of payment mechanisms on spending in two significant ways. First, we are interested in the effects of the availability of credit on spending, and not necessarily in the effect of the transaction format that is associated with each payment mechanism. Second, while prior research has studied the point-of-purchase and historic (i.e., prepurchase) effects of credit, the present research is concerned with the availability of credit in the future. Specifically, our framework is invariant to the current and prior usage of credit by the consumer.

Behaviorally Informed Policies for Household Financial Decisionmaking
Low incomes, limited financial literacy, fraud, and deception are just a few of the many intractable economic and social factors that contribute to the financial difficulties that households face today. Addressing these issues directly is difficult and costly. But poor financial outcomes also result from systematic psychological tendencies, including imperfect optimization, biased judgments and preferences, and susceptibility to influence by the actions and opinions of others. Some of these psychological tendencies and the problems they cause may be countered by policies and interventions that are both low cost and scalable. We detail the ways that these behavioral factors contribute to consumers’ fiancial mistakes and suggest a set of interventions that the federal government, in its dual roles as regulator and employer, could feasibly test or implement to improve household financial outcomes in a variety of domains: retirement, short-term savings, debt management, the take-up of government benefits, and tax optimization.
