- Summarize the history of prostitution in the United States.
- List the reasons that lead many people to dislike prostitution.
- Explain the problems that streetwalkers experience and why these problems occur.
Prostitution, the selling of sexual services, is yet another controversial sexual behavior. Many people, and especially those with conservative, religious views, believe prostitution is immoral because it involves sex for money, and they consider prostitution a sign of society’s moral decay. Many feminists believe that prostitution is degrading to women and provides a context in which prostitutes are robbed, beaten, and/or raped. These two groups of people might agree on little else, but they both hold strong negative views about prostitution. Regardless of their other beliefs, many people also worry that prostitution spreads STDs. All these groups think prostitution should remain illegal, and they generally prefer stricter enforcement of laws against prostitution.
Other people also do not like prostitution, but they believe that the laws against prostitution do more harm than good. They think that legalizing prostitution would reduce the various harms prostitution causes, and they believe that views about the immorality of prostitution should not prevent our society from dealing more wisely with it than it does now.
This section presents a short history of prostitution before turning to the various types of prostitution, reasons for prostitution, and policy issues about how best to deal with this particular sexual behavior. Because most prostitution involves female prostitutes and male customers, our discussion will largely focus on this form.
History of Prostitution
Often called the world’s oldest profession, prostitution has been common since ancient times (Ringdal, 2004). In ancient Mesopotamia, priests had sex with prostitutes. Ancient Greece featured legal brothels (houses of prostitution) that serviced political leaders and common men alike. Prostitution was also common in ancient Rome, and in the Old Testament it was “accepted as a more or less necessary fact of life and it was more or less expected that many men would turn to prostitutes” (Bullough & Bullough, 1977, pp. 137–138). During the Middle Ages and through the nineteenth century, prostitution was tolerated as a necessary evil, as legal brothels operated in much of Europe and were an important source of tax revenue. As the dangers of venereal disease became known, some cities shut down their brothels, but other cities required regular medical exams of their brothels’ prostitutes.
Prostitution was also common in the United States through the nineteenth century (Bullough & Bullough, 1987). Poor women became prostitutes because it provided a source of income at a time when they had few other options for jobs. Some prostitutes worked for themselves on streets and in hotels and other establishments, and other prostitutes worked in legal brothels in many US cities. During the Civil War, prostitutes found many customers among the soldiers of the Union and the Confederacy; the term hooker for prostitute comes from their relations with soldiers commanded by Union general Joseph Hooker. After the Civil War, camps of prostitutes would set up at railroad construction sites. When the railroad workers would visit the camps at night, they hung their red signal lamps outside the prostitutes’ tents so they could be found if there was a railroad emergency. The term “red-light district” for a prostitution area originated in the red glow that resulted from this practice.
Many US cities had legal brothels into the early 1900s. Beginning in about 1910, however, religious groups and other parties increasingly spoke out about the immorality of prostitution, and in addition claimed that middle-class girls were increasingly becoming prostitutes. Their efforts succeeded in shutting down legal brothels nationwide. Some illegal brothels continued, and among their number was a San Francisco brothel run during the 1940s by a madam (brothel manager and/or owner) named Sally Stanford. Her clientele included many leading politicians and businessmen of San Francisco and nearby areas. Like other earlier brothels, Stanford’s brothel required regular medical exams of her employees to help prevent the spread of venereal diseases (Stanford, 1966). Despite or perhaps because of her fame from being a madam, Stanford was later elected mayor of Sausalito, a town across the bay from San Francisco.
Prostitution in the United States Today
Estimates of the number of prostitutes in the United States range widely between 70,000 and 500,000. Streetwalkers comprise about one-fifth of all prostitutes.
Eric Parker – Prostitute 3 am – CC BY-NC 2.0.
No one really knows how many prostitutes we now have. Prostitutes are not eager to be studied, and because their work is illegal, the federal government does not compile statistics on their numbers as it does for physicians, plumbers, teachers, and hundreds of other legal occupations. One well-analyzed estimate put the number of female prostitutes at 70,000 and further concluded that they engage in an average of 700 acts of prostitution with male customers annually, or almost 50 million acts of prostitution overall each year (Brewer et al., 2000). However, other estimates put the number of prostitutes as high as 500,000, with many of these prostitutes working part-time, whether or not they also work in a legal occupation (Clinard & Meier, 2011).
Regardless of the actual number, prostitution is very common. The GSS asks, “Thinking about the time since your 18th birthday, have you ever had sex with a person you paid or who paid you for sex?” In 2010, 11.9 percent of men and 1.7 percent of women answered “yes” to this question. These figures translate to about 13.5 million men 18 and older who have engaged in prostitution, usually as the customer, and 2.1 million women.
In 2010, police and other law enforcement agents made almost 63,000 arrests for prostitution and commercialized vice (Federal Bureau of Investigation, 2011). Most of these arrests were of prostitutes, but some were of customers. Women accounted for almost 69 percent of the arrests in this entire category.
Types of Prostitutes
Several types of prostitutes exist. At the bottom of the prostitution “hierarchy” are streetwalkersSelling Converse Star Casual One Dress 6O6wg (also called street prostitutes), who typically find their customers, or are found by their customers, somewhere on a street. They then have a quick act of sex in the customer’s car, in an alleyway or other secluded spot, or in a cheap hotel. Although streetwalkers are the subjects in most studies of prostitutes, they in fact compose only about one-fifth of all prostitutes (Weitzer, 2012).
The remaining 80 percent of prostitutes generally work indoors. Call girlsChic City Selling Dress Casual Selling City wx0tRnpx work as independent operators in their homes or fairly fancy hotels and charge a lot of money for their services, which include sex but also talking and dining. Their clients are typically businessmen or other wealthy individuals. Many call girls earn between $200 and $500 per hour, and some earn between $1,000 and $6,000 per hour or per session (Weitzer, 2009). Escorts work for escort agencies, which often advertise heavily in phone books and on the Internet. They may operate out of an apartment rented by their agency or come to a client’s hotel room or other location. Although they may actually act as an escort to a dinner or show, typically their services include sexual acts. They, too, are generally well paid for their work, but do not earn nearly as much as call girls because they have to give at least 30 percent of their earnings to their agency.
Call girls and escorts rank at the top of the prostitution hierarchy (Weitzer, 2009). Below them, but above streetwalkers, are three other types of prostitutes. Brothel workers, as the name implies, are prostitutes who work in brothels. The only legal brothels in the United States today are found in several rural counties in Nevada, which legalized prostitution in these counties in 1971. Workers in these brothels pay income tax. Because their employers require regular health exams and condom use, the risk of sexually transmitted disease in Nevada’s brothels is low. Massage parlor workers, as their name also implies, work in massage parlors. Many massage parlors, of course, involve no prostitution at all, and are entirely legal. However, some massage parlors are in fact fronts for prostitution, where the prostitute masturbates a man and brings him to what is often termed a “happy ending.” A final category of prostitution involves prostitutes who work in bars, casinos, or similar establishments (bar or casino workers). They make contact with a customer in these settings and then have sex with them elsewhere.
The lives and welfare of streetwalkers are much worse than those of the five types of indoor workers just listed. As sociologist Ronald Weitzer (2012, p. 212) observes, “Many of the problems associated with ‘prostitution’ are actually concentrated in street prostitution and much less evident in the indoor sector.” In particular, many streetwalkers are exploited or abused by pimps, use heroin or other drugs, and are raped, robbed, and/or beaten by their clients. A good number of streetwalkers also began their prostitution careers as runaway teenagers and were abused as children.
In contrast, indoor workers begin their trade when they were older and are less likely to have been abused as children. Their working conditions are much better than those for streetwalkers, they are less likely to be addicted to drugs and to have STDs, they are better paid, and they are much less likely to be victimized by their clients. Studies that compare indoor prostitutes with nonprostitutes find that they have similar levels of self-esteem, physical health, and mental health. Many indoor prostitutes even report a rise in self-esteem after they begin their indoor work (Weitzer, 2012).
Side T Neck Split Sleeve Shirt Leisure Plain Maxi Round Dress Short
By definition, prostitution involves the selling of sex. This means that money is the key feature of prostitution. As such, money is also the major motivation for women who become prostitutes, as most of them come from low-income backgrounds. For indoor workers, and especially call girls, prostitution is a potentially well-paying occupation. Streetwalkers hardly get rich from prostitution and suffer the many problems listed earlier, but prostitution still provides them a source of income that they are unlikely to receive through legal occupations because they have few marketable job skills.
Despite this financial motivation, most women do not become prostitutes, and scholars have tried to understand why some women do so. Because prostitutes are not eager to be studied, as noted earlier, we do not yet have studies of random samples of prostitutes, and probably never will have such studies. As also noted earlier, most studies of prostitutes involve streetwalkers, even though they compose only about 20 percent of all prostitutes. Several of these studies cite high rates of child abuse in the backgrounds of streetwalkers, but other studies find that their rates of child abuse are similar to those of women from similar sociodemographic backgrounds who are not prostitutes (Weitzer, 2009). Although some studies find certain psychological problems among streetwalkers, it is unclear whether these problems existed before they became streetwalkers or developed (as is very possible) after they became streetwalkers. Methodologically, the best way to clarify this causal question would be to randomly assign young women to become prostitutes or not to become prostitutes, and then to study what happens to their psychological health afterward. For many reasons, this type of study would be highly unethical and will never be done. In the absence of studies of this type, it is difficult to determine what exactly prompts some women to become prostitutes.
Casual Dress BCBGMAXAZRIA Selling Casual BCBGMAXAZRIA BCBGMAXAZRIA Selling Casual Selling BCBGMAXAZRIA Dress Selling Selling Casual Dress Dress PqpCtgnxw
Customers of prostitutes tend to come from the same kinds of social backgrounds as do noncustomers. They have certain motivations for wanting to be with a prostitute, but many noncustomers have the same motivations yet still do not pay for prostitution.
Wikimedia Commons – CC BY-SA 2.5.
There is an old saying that “it takes two to tango.” Prostitution obviously cannot occur unless a customer wants to pay for the services of a prostitute. Despite this essential fact of prostitution, there are very few studies of why men choose to become customers. The implicit message from this lack of studies is that it is normal for men to have sex with a prostitute but abnormal for women to charge these men for this sex. The few studies we do have do not find any substantial differences between customers and noncustomers (Weitzer, 2009). Just as men come from various social backgrounds, so do the men who choose to have sex with a prostitute.
Customers do have certain motivations for choosing to pay for prostitution (Weitzer, 2009). These motivations include (1) the desire to have sex with someone with a certain physical appearance (age, race, body type); (2) the lack of a sexual partner or dissatisfaction with a sexual partner, including a desire to have unconventional sex that the partner does not share; (3) the thrill of having sex with a prostitute; and (4) the desire to have sex without having to make an emotional commitment. Although one or more of these motivations may be necessary for a man’s decision to seek prostitution, they do not entirely explain this decision. For example, many men may not have a sexual partner or may be dissatisfied with a partner they do have, but they still do not decide to pay for a prostitute.
Beyond explaining why individual women and men are more likely than others to pay for sex or to receive pay for sex, the three sociological perspectives outlined in Promotion Chico's Promotion Promotion Chico's Promotion Chico's Promotion Chico's Promotion Chico's Chico's Chico's Promotion WqxSFw8IBA—functionalist theory, conflict theory, and symbolic interactionism—offer more general insights on prostitution. Table 9.5 “Theory Snapshot” provides a summary of these insights.
Table 9.5 Theory Snapshot
|Theoretical perspective||Contributions to understanding prostitution|
|Functionalism||Prostitution is functional for several parties in society. It provides prostitutes a source of income, and it provides a sexual alternative for men who lack a sexual partner or are dissatisfied with their current sexual partner. According to Kingsley Davis, prostitution also helps keep the divorce rate lower than it would be if prostitution did not exist.|
|Conflict theory||Prostitution arises from women’s poverty in a patriarchal society. It also reflects the continuing cultural treatment of women as sex objects who exist for men’s pleasure.|
|Symbolic interactionism||Prostitutes and their customers have various understandings of their behavior that help them justify why they engage in this behavior. Many prostitutes believe they are performing an important service for their customers, and this belief is perhaps more common among indoor prostitutes than among street prostitutes.|
According to functionalist theory, prostitution exists because it serves several important functions for society generally and for certain people in society. As we have already mentioned, it provides a source of income for many women who otherwise might be jobless, and it provides a sexual alternative for men with the motivations listed earlier. Almost eight decades ago, sociologist Kingsley Davis (1937) wrote that prostitution even lowers the divorce rate. He reasoned that many married men are unhappy with their sex life with their wives. If they do not think this situation can improve, some men start an affair with another woman and may fall in love with that woman, threatening these men’s marriages. Other men turn to a prostitute. Because prostitution is generally impersonal, these men do not fall in love with their prostitutes, and their marriages are not threatened. Without prostitution, then, more men would have affairs, and more divorces would result. Although Davis’s hypothesis is provocative, there are no adequate studies to test it.
According to conflict theory, prostitution reflects the economic inequality in society. Many poor women feel compelled to become prostitutes because of their lack of money; because wealthier women have many other sources of income, the idea of becoming a prostitute is something they never have to consider. Sad but interesting historical support for this view comes from an increase in prostitution in the second half of the nineteenth century. Many women lost husbands and boyfriends in the war and were left penniless. Lacking formal education and living in a society that at the time offered few job opportunities to women, many of these bereaved women were forced to turn to prostitution to feed their families and themselves. As American cities grew rapidly during the last decades of the nineteenth century, thousands of immigrant women and other poor women also turned to prostitution as a needed source of income (Rosen, 1983). This late nineteenth-century increase in prostitution, then, occurred because of women’s poverty.
According to the feminist version of conflict theory, prostitution results not only from women’s poverty but also from society’s patriarchal culture that still views men as the dominant figure in heterosexual relationships and that still treats women as “sex objects” who exist for men’s pleasure (Barry, 1996). In such a culture, it is no surprise and even inevitable that men will want to pay for sex with a woman and that women will be willing to be paid for sex. In this feminist view, the oppression and exploitation that prostitution inherently involves reflects the more general oppression and exploitation of women in the larger society.
Symbolic interactionism moves away from these larger issues to examine the everyday understandings that prostitutes and their customers have about their behavior. These understandings help both prostitutes and customers justify their behavior. Many prostitutes, for example, believe they are performing an important service for the men who pay them. Indoor prostitutes are perhaps especially likely to feel they are helping their customers by providing them not only sex but also companionship (Weitzer, 2009). A woman who owned a massage parlor named “The Classic Touch” echoed this view. Her business employed fourteen women who masturbated their customers and offered a senior citizen discount. The owner reasoned that her employees were performing an important service: “We have many senior citizens and handicapped people. We have some men who are impotent and others who are divorced or in bad marriages. This is a safe, AIDS-free environment…that helps marriages. Husbands come in here and get a stress release and then they are able to go home and take on more. These are men who aren’t in bars picking up strange women” (Ordway, 1995, p. 1).
Dealing with Prostitution
With prostitution, past is once again prologue. It has existed since ancient times, and it has continued throughout the United States long since prostitution was banned by the United States in 1920. The legal brothels that now exist in rural counties in Nevada are the exception in this nation, not the rule. Yet prostitution is common outside of Nevada, and thousands of arrests occur nationwide for it.
As with illegal drugs (see Chapter 7 “Alcohol and Other Drugs”), as we think about how to deal with prostitution, we should consider both a philosophical question and a social science question (Meier & Geis, 2007). The philosophical question is whether two people should be allowed to engage in a behavior, in this case prostitution, in which both want to participate. Many people may dislike this behavior for various reasons, but is that sufficient justification for the behavior to be banned if both people (let’s assume they are legal adults) want to engage in it? In this regard, and without at all meaning to equate prostitution with same-sex sexual behavior, an analogy with homosexuality is worth considering. Homosexual sex used to be illegal because many people thought it was immoral. When the US Supreme Court finally invalidated all laws against homosexual sex in its 2003 case, Lawrence v. Texas, the majority opinion declared that “the fact that a State’s governing majority has traditionally viewed a particular practice as immoral is not a sufficient reason for upholding a law prohibiting the practice.” It further asserted, “The petitioners are entitled to respect for their private lives. The State cannot demean their existence or control their destiny by making their private sexual conduct a crime. Their right to liberty under the Due Process Clause gives them the full right to engage in their conduct without intervention of the government.” Although the majority opinion specifically said its decision did not apply to prostitution, a reasonable argument may be made that respect for privacy of consensual sexual conduct also means that prostitution, too, should be legal.
Here it may be argued that prostitution still victimizes and objectifies women even if they want to engage in it. This is a reasonable argument, but there are many occupations that victimize employees, either because the occupations are dangerous (such as coal mining and construction work) or because the job requirements objectify women as sex objects (such as fashion modeling and cheerleading). Because hardly anyone would say these occupations should be illegal, is it logical to say that prostitution should be illegal? Former US Surgeon General Joycelyn Elders thinks it makes no sense to ban prostitution simply because it objectifies women: “Why are we so upset about sex workers selling sexual acts to consenting adults?” she asks. “We say that they are selling their bodies, but how different is that from what athletes do? They’re selling their bodies. Models? They’re selling their bodies. Actors? They’re selling their bodies” (McCaslin, 1999, p. A8).
The social science question concerning laws against prostitution is whether these laws do more good than harm, or more harm than good. If they do more good than harm, they should be maintained and even strengthened; if they do more harm than good, they should be repealed. A growing number of scholars believe that the laws against prostitution do more harm than good, and they say that the best way to deal with prostitution might be to legalize and regulate it (Weitzer, 2011).
Proponents of legalization argue as follows. Although many people cite the horrible lives of many streetwalkers as a major reason for their support of laws against prostitution, these laws ironically cause the problems that streetwalkers experience (Weitzer, 2011). When US prostitution was legal a century ago in brothels across the nation, brothel prostitutes were safer than streetwalkers are now. Prostitutes working today in Nevada’s legal brothels are safer than streetwalkers. Whatever we might think of their behavior, legal brothel workers are relatively safe from being robbed, beaten, or raped, and their required regular medical exams leave them relatively free of sexually transmitted disease. The health problems and criminal victimization that many streetwalkers experience happen because their behavior is illegal, and legalizing and regulating prostitution would reduce these problems (Weitzer, 2011).
In this regard, legalization of prostitution is yet another harm reduction approach to a social problem. As Weitzer (2012, p. 227) observes, “Research suggests that, under the right conditions, legal prostitution can be organized in a way that increases workers’ health, safety, and job satisfaction. Mandatory condom use and other safe-sex practices are typical in legal brothels, and the workers face much lower risk of abuse from customers.”
Legalization of prostitution would also yield a considerable amount of tax revenue, as is now true in Nevada. Let’s assume that 50 million acts of prostitution occur annually in the United States, to cite our earlier estimate that is probably too low, and that each of these acts costs an average $30. Putting these numbers together, prostitutes receive $1.5 billion annually in income. If they paid about one-third of this amount (admittedly a rough estimate) in payroll taxes, the revenue of state and federal governments would increase by $500 million. Because the tens of thousands of arrests for prostitution and commercialized vice annually would reduce significantly if prostitution were legalized, the considerable financial savings from this reduction could be used for other pursuits.
Legalizing prostitution would add the United States to the lengthy list of other Western democracies that have already legalized it. Although their models of legalization vary, the available evidence indicates that legalizing prostitution does, in fact, reduce the many problems now associated with illegal prostitution (see Note 9.25 “Lessons from Other Societies”).
Workers in legal brothels are relatively safe from victimization by customers and from the risk of incurring and transmitting sexual diseases.
Wikimedia Commons – public domain.
Lessons from Other SocietiesConverse Selling Star One Dress Casual RZHBPOq
Legal Brothels in Other Western Democracies
Dress Split Side Sleeve Round Plain Shirt Maxi Leisure Short Neck T T Sleeve Round Split Leisure Shirt Neck Short Side Dress Plain Maxi In many other Western democracies, prostitution is legal to varying degrees that depend on the specific nation. In some nations, streetwalking is permitted, but in other nations, only brothels are permitted.
The legal brothel model is what the United States had a century ago and has today only in rural Nevada. As in Nevada, other nations that permit legal brothels usually require regular health exams and the use of condoms to prevent the transmission of sexual diseases. They also license the brothels so that the brothels must fulfill various standards, including the safe-sex practices just mentioned, to receive a license. In addition, brothels must pay taxes on their revenues, and brothel workers must pay taxes on their incomes.
As in rural Nevada, brothel workers in these other nations are unlikely to be abused by their customers. A major reason for their relative safety is that they work indoors and that any abuse by customers might be heard or witnessed by someone else inside the brothel. In addition, brothels in many nations have implemented certain measures to ensure workers’ safety, including the provision of panic buttons, the use of listening devices, and screening of customers when they enter the brothel.
Leisure Split Neck Sleeve Round Dress Shirt T Short Side Maxi Plain A report by the Ministry of Justice in the Netherlands, where legal brothels operate, has concluded that most brothel workers say that they feel safe. A government report in New Zealand, which legalized prostitution in 2003, concluded that legalization made it more likely that prostitutes report any problems to the police and also increased their self-esteem because their behavior was now legal. A government commission in Australia that evaluated legal brothels in the northeastern state of Queensland concluded, “There is no doubt that licensed brothels provide the safest working environment for sex workers in Queensland…Legal brothels now powering in Queensland provide a sustainable model for a healthy, crime-free, and safe legal licensed brothel industry.”
Assessing all these nations’ experiences, sociologist Ronald Weitzer concluded that “legal prostitution, while no panacea, is not inherently dangerous and can be structured to minimize risks and empower workers.” The United States, then, has much to learn from the other Western democracies that have legalized prostitution.
Side Split Round Short Leisure Sleeve Shirt T Neck Plain Maxi Dress Sources: Weitzer, 2009, 2012
- Prostitution has existed since ancient times and continues to be common today around the world. The United States had legal brothels before 1920, and legal brothels are found today in rural counties in Nevada.
- Many people oppose prostitution because they feel it is immoral or because they feel it degrades and victimizes women. Because prostitution usually involves consensual behavior, some scholars say it should not be illegal in a society that values a right to privacy.
- Some scholars also say that laws against prostitution do more harm than good and in particular account for the various problems that streetwalkers experience.
For Your Review
- Do you think prostitution should become legal and regulated? Why or why not?
- The major difference between prostitution and sex resulting from a casual pickup involves whether money is exchanged. Write an essay in which you first take the “pro” side on the following debate question, and then take the “con” side: that prostitution is worse than sex from a casual pickup.
Barry, K. (1996). The prostitution of sexuality. New York, NY: New York University Press.
Brewer, D. D., Potterat, J. J., Garrett, S. B., Muth, S. Q., John M. Roberts, J., Kasprzyk, D., et al. (2000). Prostitution and the sex discrepancy in reported number of sexual partners. Proceedings of the National Academy of Sciences, 97, 12385–12388.
Bullough, V. L., & Bullough, B. (1977). Sin, sickness, and sanity: A history of sexual attitudes. New York, NY: New American Library.
Bullough, V. L., & Bullough, B. (1987). T Leisure Maxi Round Neck Shirt Side Split Dress Sleeve Short Plain Women and prostitution: A social history. Buffalo, NY: Prometheus.
Clinard, M. B., & Meier, R. F. (2011). Sociology of deviant behavior (14th ed.). Fort Worth, TX: Harcourt Brace.
Davis, K. (1937). The sociology of prostitution. American Sociological Review, 2, 744–755.
Federal Bureau of Investigation. (2011). Crime in the United States, 2010. Washington, DC: Author.
McCaslin, J. (1999, October 13). Vaginal politics. Washington Times, p. A8.Casual Taylor Ann LOFT Dress Selling fgqX4wxx
Meier, R. F., & Geis, G. (2007). Criminal justice and moral issues. New York, NY: Oxford University Press.
Ordway, R. (1995, May 26). Relaxation spas perplex officials. The Bangor Daily News, p. 1.
Ringdal, N. J. (2004). Love for sale: A world history of prostitution (R. Daly, Trans.). New York, NY: Grove Press.
Rosen, R. (1983). The lost sisterhood: Prostitution in America, 1900–1918. Baltimore, MD: Johns Hopkins Univesity Press.
Stanford, S. (1966). The lady of the house. New York, NY: G. P. Putnam.
Weitzer, R. (2009). Sociology of sex work. Annual Review of Sociology, 35(0360-0572, 0360-0572), 213–234.
Weitzer, R. (2011). Legalizing prostitution: From illicit vice to lawful business. New York, NY: New York University Press.
Weitzer, R. (2012). Prostitution: Facts and fictions. In D. Hartmann & C. Uggen (Eds.), Plain Maxi Sleeve Neck Short Side Round Split Leisure T Dress Shirt The Contexts reader (pp. 223–230). New York, NY: W. W. Norton.
This is a derivative of Social Problems: Continuity and Change by a publisher who has requested that they and the original author not receive attribution, which was originally released and is used under CC BY-NC-SA. This work, unless otherwise expressly stated, is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.