Trade-off

A trade-off (or tradeoff is a situation that involves losing one quality, aspect or amount of something in return for gaining another quality, aspect or amount. More colloquially, if one thing increases, some other thing must decrease. Tradeoffs can occur for many reasons, including simple physics (into a given amount of space, you can fit many small objects or fewer large objects). To give an everyday example, a person packing her suitcase for a holiday, assuming the airline only allows one suitcase of a maximum size, has to make trade-offs in the items she packs. If her suitcase, in her initial packing attempt, only consisted of clothing, to add toiletries to her suitcase, every toiletry item she adds will lead to a trade-off of less clothing. The idea of a tradeoff often implies a decision to be made with full comprehension of both the upside and downside of a particular choice, such as when a person decides whether to invest in stocks (more risky but with a greater potential return) versus bonds (generally safer, but lower potential returns).

The term is also used widely in an evolutionary context, in which case natural selection and sexual selection act as the ultimate "decision-makers". In biology, the concepts of tradeoffs and constraints are often closely related. In economics, a trade-off is commonly expressed in terms of the opportunity cost of one potential choice, which is the loss of the best available alternative.

An opportunity cost example of trade-offs for an individual would be the decision by a full-time worker to take time off work with a salary of $50,000 to attend medical school, with annual tuition of $30,000. If we assume for the sake of simplicity that the medical school only allows full-time study, then the individual considering stopping work would face a trade-off between not going to medical school and earning $50,000 at work, or going to medical school and losing $50,000 in salary and having to pay $30,000 in tuition.

Examples

The concept of a trade-off is often used to describe situations in everyday life. The old saying "do not put all of your eggs into one basket" implies a trade-off with respect to spreading risk, as when one buys a mutual fund composed of many stocks rather than only one or a few stocks that may have a higher expected value of return.

Similarly, trash cans that are used inside and then taken out to the street and emptied into a Dumpster can be small or large. A large trash can does not need to be taken out to the Dumpster so often, but it may become so heavy when full that one risks back injury when trying to move it. Here the trade-off is frequency of having to put out the trash in the Dumpster against weight of can and potential for injury. If food waste is being put into a trash can, there is a second trade-off for large versus small trash cans. With a large trash can, food waste will sit for a longer time in the kitchen, attracting cockroaches and rodents. With a small trash can, the can will be taken out to the Dumpster more often, thus attracting less pests in the kitchen.

In cold climates, mittens in which all the fingers are in the same compartment serve well to keep the hands warm, but they do not allow the hands to function as well as do gloves; however, gloves, by keeping each finger separate, do not keep hands as warm. As such, with mittens and gloves, hand warmth and hand dexterity are trade-offs. In a like fashion, warm coats are often bulky and hence they impede freedom of movement for the wearer. Thin coats, such as those worn by winter sports athletes, give the wearer more freedom of movement, but they are not as warm.

When copying music from compact discs to a computer, lossy compression formats, such as MP3, are used routinely to save hard disk space, but information is "thrown away" to the detriment of sound quality. Lossless compression schemes, such as FLAC or ALAC take much more disc space, but do not affect the sound quality as much, thus providing better sound.

Large cars can carry many people (five or more), and since they have larger crumple zones, they may be safer in an accident. However they also tend to be heavy (and often not very aerodynamic) and hence have relatively poor fuel economy. Small cars like the Smart Car can only carry two people, and their light weight means they are very fuel efficient. At the same time, the smaller size and weight of small cars means that they have smaller crumple zones, which means occupants are less protected in case of an accident. In addition, if a small car has an accident with a larger, heavier car, the occupants of the smaller car will fare more poorly. Thus car size (large versus small) involves multiple tradeoffs regarding passenger capacity, accident safety and fuel economy.

In the Olympics, the best sprinters are not the same individuals as the best long-distance marathoners, a trade-off based on various morphological, physiological (e.g., variation in muscle fiber type), and possibly motivational factors.

In economics

In economics a trade-off is expressed in terms of the opportunity cost of a particular choice, which is the loss of the most preferred alternative given up. A tradeoff, then, involves a sacrifice that must be made to obtain a certain product, service or experience, rather than others that could be made or obtained using the same required resources. For example, for a person going to a basketball game, their opportunity cost is the loss of the alternative of watching a particular television program at home. If the basketball game occurs during her or his working hours, then the opportunity cost would be several hours of lost work, as she/he would need to take time off work.

Many factors affect the tradeoff environment within a particular country, including availability of raw materials, a skilled labor force, machinery for producing a product, technology and capital, market rate to produce that product on reasonable time scale, and so forth.

A trade-off in economics is often illustrated graphically by a Pareto frontier (named after the economist Vilfredo Pareto), which shows the greatest (or least) amount of one thing that can be attained for each of various given amounts of the other. As an example, in production theory the trade-off between output of one good and output of another is illustrated graphically by the production possibilities frontier. The Pareto frontier is also used in multi-objective optimization. In finance, the Capital Asset Pricing Model includes an efficient frontier that shows the highest level of expected return that any portfolio could have given any particular level of risk, as measured by the variance of portfolio return.

In other specific fields

In biology and microbiology, tradeoffs occur when a beneficial change in one trait is linked to a detrimental change in another trait.

Tradeoffs are important in engineering. For example, in electrical engineering, negative feedback is used in amplifiers to trade gain for other desirable properties, such as improved bandwidth, stability of the gain and/or bias point, noise immunity, and reduction of nonlinear distortion.

In demography, tradeoff examples may include maturity, fecundity, parental care, parity, senescence, and mate choice. For example, the higher the fecundity (number of offspring), the lower the parental care that each offspring will receive. Parental care as a function of fecundity would show a negative sloped linear graph. A related phenomenon, known as demographic compensation, arises when the different components of species life cycles (survival, growth, fecundity, etc) show negative correlations across the distribution ranges. For example, survival may be higher towards the northern edge of the distribution, while fecundity or growth increases towards the south, leading to a compensation that allows the species to persist along an environmental gradient. Contrasting trends in life cycle components may arise through tradeoffs in resource allocation, but also through independent but opposite responses to environmental conditions.

In computer science, tradeoffs are viewed as a tool of the trade. A program can often run faster if it uses more memory (a space-time tradeoff). Consider the following examples:

• By compressing an image, you can reduce transmission time/costs at the expense of CPU time to perform the compression and decompression. Depending on the compression method, this may also involve the tradeoff of a loss in image quality.
• By using a lookup table, you may be able to reduce CPU time at the expense of space to hold the table, e.g. to determine the parity of a byte you can either look at each bit individually (using shifts and masks), or use a 256-entry table giving the parity for each possible bit-pattern, or combine the upper and lower nibbles and use a 16-entry table.
• For some situations (e.g. string manipulation), a compiler may be able to use inline code for greater speed, or call run-time routines for reduced memory; the user of the compiler should be able to indicate whether speed or space is more important.

The Software Engineering Institute has a specific method for analysing tradeoffs, called the Architectural Tradeoff Analysis Method or ATAM.

Strategy board games often involve tradeoffs: for example, in chess you might trade a pawn for an improved position. In a worst-case scenario, a chess player might even tradeoff the loss of a valuable piece (even the Queen) to protect the King. In Go, you might trade thickness for influence.

Ethics often involves competing interests that must be traded off against each other, such as the interests of different people, or different principles (e.g. is it ethical to use information resulting from Nazi human medical experiments in death camps to prevent disease today?)

In medicine, patients and physicians are often faced with difficult decisions involving tradeoffs. One example is localized prostate cancer where patients need to weigh the possibility of a prolonged life expectancy against possible stressful or unpleasant treatment side-effects (patient trade-off).

Governmental tradeoffs are among the most controversial political and social difficulties of any time. All of politics can be viewed as a series of tradeoffs based upon which core values are most core to the most people or politicians. Political campaigns also involve tradeoffs, as when attack ads may energize the political base but alienate undecided voters.

With work schedules, employees will often use a tradeoff of "9/80" where an 80-hour work period is compressed from a traditional 10 working days to nine to get every second Friday off.

See also

• Architecture tradeoff analysis method
• Biological constraints
• Carrier's constraint
• Detection error tradeoff
• Evolutionary medicine
• Evolutionary physiology
• Pareto front
• Patient trade-off
• Space–time tradeoff
• Time-trade-off
• Trade-off theory of capital structure
• Williamson trade-off model

Further reading

• Albuquerque, R. L. de, K. E. Bonine, and T. Garland, Jr. 2015. Speed and endurance do not trade off in phrynosomatid lizards. Physiological and Biochemical Zoology 88:634–647.
• Alexander, R. McN. 1985. The ideal and the feasible: physical constraints on evolution. Biol. J. Linn. Soc. 26:345-358.
• Bennett, A. F., Lenski, R. E. 2007. An experimental test of evolutionary trade-offs during temperature adaptation. Proc. Natl. Acad. Sci. USA 104:8649-8654.
• Campbell, D. E., and J. S. Kelly. 1994. Trade-off theory. The American Economic Review 84:422-426.
• Haak, D. C., McGinnis, L. A., Levey, D. J., Tewksbury, J. J. 2012. Why are not all chilies hot? A trade-off limits pungency. Proc. R. Soc. B Biol. Sci. 279:2012-2017.
• Roff, D. A., Fairbairn, D. J. 2007. The evolution of tradeoffs: where are we? J. Evol. Biol. 20:433-447.
• Stearns, S. C. 1989. Trade-offs in life-history evolution. Functional Ecology 3:259-268.
• Philipson, C. D. et al. (2014). A trait-based trade-off between growth and mortality: evidence from 15 tropical tree species using size-specific relative growth rates. Ecology & Evolution 4: 3675–3688. 10.1002/ece3.1186 10.1002/ece3.1186