This is an appeal from a judgment dismissing the complaint of the plaintiff by the circuit court. On December 12, 1980, Circuit Judge James H. Levi dismissed plaintiff’s (Marshfield Clinic) complaint on the ground that no cause of action existed to hold a wife liable for the necessary medical expenses of her husband. The court of appeals certified the appeal to this court pursuant to sec. 809.61, Stats. 1979-80. We granted certification to consider whether a wife is liable for medical expenses incurred by her deceased husband *508on his own behalf in the absence of her agreement to accept responsibility for the expenses.
The record in this case is almost totally devoid of facts because the trial court dismissed the complaint without making any findings. From the limited record, it is clear that the plaintiff provided medical services to Theodore Discher, the defendant’s husband, from November 18, 1978 to April 15, 1979, the date of his death. The plaintiff alleged it had not been paid for these services. However, the plaintiff did not allege that any attempts were made to collect from the estate of the husband or that the husband’s estate had no assets.
The trial court dismissed this action before it was aware of our recent decisions in Sharpe Furniture, Inc. v. Buckstaff, 99 Wis. 2d 114, 299 N.W.2d 219 (1980), and In Matter of Estate of Stromsted, 99 Wis. 2d 136, 299 N.W.2d 226 (1980). These eases represent a significant development in the common law necessaries doctrine in this state. In Sharpe this court held that the necessaries doctrine remains an important part of the common law today and that a husband may be held liable for necessary items bought by his wife on credit. The issue in Stromsted involved the related question of whether a wife may also be liable for necessaries furnished to her in the absence of any express contract. We held in Strom-sted that a wife may be held liable for the family’s necessaries along with the husband, but that the husband was primarily liable while the wife was secondarily liable. The present case deals with a situation where the necessary services were rendered to the husband and the creditor seeks to collect from the wife.
Our holding in Stromsted makes it clear that a wife shares with her husband a limited legal duty of support of the family. Stromsted, supra, 99 Wis. 2d at 143. This includes liability for necessary medical expenses in*509curred by either spouse. Although the husband is primarily liable “ [t] o the extent that the husband is unable to satisfy his obligation in this regard, the creditor may seek satisfaction from the wife.” Stromsted, supra, 99 Wis. 2d at 145. If the plaintiff in this case had proven that it had attempted to collect from Mr. Discher’s estate, but had been unable to do so, Mrs. Discher would be liable. However no such showing was made or even attempted. Therefore, we remand to give the plaintiff an opportunity to prove that it either attempted to collect from Mr. Discher’s estate but was unable to do so, or that any collection attempts would have been futile. If the plaintiff is able to make such a showing then it will be able to proceed against Mrs. Discher under the Strom-sted rule. But we re-emphasize that the Stromsted rule only applies in the absence of an express agreement by the parties.1 If it appears on remand that the clinic had expressly agreed to look only to the husband for payment of his medical expenses, then Mrs. Discher cannot be liable.
The argument has been raised in this case that the Stromsted rule is unconstitutional because it discriminates on the basis of gender and therefore violates equal protection. This issue was not raised in Stromsted and we declined to address any potential constitutional claims. Stromsted, supra, 99 Wis. 2d at 140, n. 3. We now hold that the rule does satisfy the test set forth in recent United States Supreme Court decisions dealing with gender based classifications.
To satisfy a constitutional challenge, a gender based rule must serve important governmental objectives and *510the means employed must he substantially related to the achievement of those objectives.2
In considering the necessaries rule, as articulated in Sharpe and Stromsted, it is apparent that it serves several important governmental objectives. The rule benefits families by making it more likely that they will obtain necessary and appropriate goods and services. It enables wives to obtain credit more easily, rather than having to depend on their husbands to make necessary purchases. It also protects wives from economic hardship by placing primary liability on husbands. This is significant because, as discussed below, wives have made substantial economic gains in the past decade, but substantial economic disparities still persist between husbands and wives. The rule also benefits the providers of goods and services by assuring them greater certainty of payment when they extend credit to. families.
The rule set forth in Sharpe and Stromsted is substantially related to the achievement of these goals. As we said in Sharpe:
“We are of the opinion that the doctrine of necessaries serves a legitimate and proper purpose in our system of common law. The heart of this common law rule is a concern for the support and the sustenance of the family and the individual members thereof. The sustenance of the family unit is accorded a high order of importance in the scheme of Wisconsin law. It has been codified as a part of our statutes, see e.g., sec. 767.08, Stats., and it has been recognized as a part of our case law. See Zachman v. Zachman, 9 Wis. 2d 335, 338, 101 N.W.2d 55 (1960). The necessaries rule encourages the extension of credit to those who in an individual capacity may not *511have the ability to make these basic purchases. In this manner it facilitates the support of the family unit and its function is in harmony with the purposes behind the support laws of this state. The rule retains a viable role in modern society.” 99 Wis. 2d at 119.
The rule benefits both the family members and the providers of goods and services. This is especially true in cases dealing with medical care. A patient may need immediate care in an emergency and the hospital must act without delay. In many cases a patient may be injured or otherwise be physically or mentally unable to agree to pay when entering the hospital. The hospital can be fortified by knowing that it can rely on either spouse to pay for medical expenses. This will allow a hospital to render immediate care without being encumbered by having to make financial arrangements at that time.
While the necessaries doctrine remains important in modern society, it is clear from Stromsted, supra, 99 Wis. 2d 136, that the old common law rule, whereby the husband was solely responsible for his family’s necessities, is out of touch with the changing role of women. Thus, Stromsted held that wives share with their husbands the legal duty of support of the family. Stromsted, supra, 99 Wis. 2d at 143. But it is also inappropriate to impose this obligation in the form of joint and several liability on the husband and the wife. Although many more married women are now working than were in the past, they still contribute less to the typical family income than do their husbands. The most recent statistics, contained in the Monthly Labor Review for October, 1981, showed that the number of married women (with husbands present) who were working had risen by nearly six million during the 1970’s. This was the largest increase in the number of working wives in any decade in United States history. By March, 1980, 24.4 million wives — half of all wives sixteen years and over — were *512working or looking for work.3 Despite these dramatic gains, the average working wife contributed only about one-fourth of the family’s income.4 While this is a substantial part of the total family income, “their average share has not changed in at least two decades.”5 In fact, there is some evidence to show that the contribution of working wives to total family income has remained rather constant over an even longer period of time. A study of working wives in Manchester, New Hampshire in 1920 showed that they earned only about one-fourth of their families’ income. This is the same proportion as indicated by the current studies throughout the United States in the late 1970’s.6
The relatively constant overall contribution by working wives to their families’ income seems partly attributable to the wide gap between average male and female earnings. Through 1978, women who worked full time earned only about 60 percent as much as men.7 Women are still concentrated in low paying jobs. A study on changing marital characteristics of workers during the 1970’s indicates that “[d] espite slight increases in the proportion of wives in higher paying professional-technical and managerial jobs, about 8 of 4 working wives were employed in lower paying clerical, service, operative, and retail sales jobs in March 1978 — about the same proportion as 8 years earlier.”8
Equally as important for our purposes is the fact that many wives still do not work outside the home at all and *513many others work only part time. If approximately half of all married women work, then obviously half do not work outside the home. Further, a recent study reveals that “[a]bout two thirds of the wives in multiearner families worked 40 weeks or more during the year, mostly full time.”9 This indicates that roughly one-third of those wives that did work only worked part time.
Taken as a whole, these figures show that, while many more wives are working in income producing jobs than ever before, the husband is still the dominant income source in the vast majority of families. Despite major increases in the number of working wives, approximately one-half of the wives do not work outside the home. Of those that do, about one-third only work part time. Working women still make far less than men do, on the average. Working wives typically contribute no more to the total family income now than they did two decades ago. In light of these facts we consider the Stromsted rule to be the most appropriate way to apportion responsibility for the family’s necessaries. A rule imposing joint and several liability on both parties, such as was adopted in Cooke v. Adams, 183 So. 2d 925 (Miss. 1966), seems very unfair if applied to the facts of this case. Similarly, the rule adopted by the New Jersey Supreme Court in Jersey Shore, Etc., v. Estate of Baum, 84 N.J. 137, 417 A.2d 1003 (1980), seems to impose too great a burden on the wife. In that case the court held that in the absence of an agreement to the contrary, the income and property of one spouse should not be exposed to satisfy debts incurred by the other spouse unless the assets of the spouse who incurred the debt are insufficient. Such a rule is preferable to joint and several liability, but it may still burden a wife by forcing her to exhaust all her assets before liability may be imposed upon the husband for a necessary expenditure incurred by her. If *514her assets are much less than her husband’s, as seems typical, then the New Jersey rule would unfairly burden his wife.
The suggestion has also been made that such cases should be decided on a case-by-case basis, imposing liability on whichever spouse has greater resources. This method would be truly gender neutral and would not face any constitutional challenges. But a case-by-case method would cause more problems than it would solve in this area. Such a rule would destroy any certainty on the part of providers of goods and services. How is the seller of goods to know which spouse possesses the greatest financial resources in any individual situation?
The Stromsted rule lets a creditor know how to proceed in collecting for necessary expenses incurred by either spouse. The creditor does not have to delve into a family’s financial background in order to ascertain from which spouse it can collect. Under Stromsted it is clear that both spouses are liable, but that a creditor must initially proceed against the husband. Such a fixed rule is essential in the commercial world.
We do not view this rule as one which “denigrates the efforts of women who contribute to the finances of their families.”10 Nor do we feel that it is paternalistic or based on an “archaic and overbroad generalization.” Schlesinger v. Ballard, 419 U.S. 498, 508 (1975). Rather, we feel that this rule accurately reflects the position of married women in contemporary society. The old common law rule that only the husband was liable for his family’s necessaries is certainly not suited to today’s societal and constitutional requirements. Yet it is also true that, despite great progress, married women still lag far behind their husbands in earning power. This *515may be due to any number of reasons, such as: discrimination that still exists in the job market; a socialized tendency for women to choose lower paying jobs; the fact that many married women still do not work outside the home, or at least work only part time. For the purposes of this case, these reasons are irrelevant. What is relevant is the verifiable fact that wives are still far from equal with their husbands in economic resources. Because of this inequality the Stromsted rule imposes primary liability upon husbands.
The United States Supreme Court has not upheld classifications based on gender when the classifications “. . . ‘command [s] “dissimilar treatment for men and women who are . . . similarly situated,” ....’” Schlesinger v. Ballard, 419 U.S. 498, 506 (1975). But when the classification reflects the demonstrable fact that men and women are not similarly situated in a certain respect, then the classification has been upheld. Schlesinger at 508. This was the case in Schlesinger where a statute treated male Navy officers differently from female officers in regard to promotions, allowing women officers a longer period of service than male officers before they would face mandatory discharge for failure to be promoted. The statute was upheld on the ground that male and female officers were not similarly situated because male officers had more opportunities to become promoted by serving in combat, which was not as readily available to female officers.
In Kahn v. Shevin, 416 U.S. 351 (1974), a Florida statute which granted a $500 property tax exemption to widows, but not to widowers, was upheld. Writing for the court, Judge DOUGLAS stated at pp. 353-54:
“There can be no dispute that the financial difficulties confronting the lone woman in Florida or in any other State exceed those facing the man. Whether from overt discrimination or from the socialization process of a *516male-dominated culture, the job market is inhospitable to the woman seeking any but the lowest paid jobs. There are, of course, efforts under way to remedy this situation. On the federal level, Title VII of the Civil Rights Act of 1964 prohibits covered employers and labor unions from discrimination on the basis of sex, 78 Stat. 253, 42 U.S.C. secs. 2000e-2(a), (c), as does the Equal Pay Act of 1963, 77 Stat. 56, 29 U.S.C. sec. 206(d). But firmly entrenched practices are resistant to such pressures, and, indeed, data compiled by the Women’s Bureau of the United States Department of Labor show that in 1972 a woman working full time had a median income which was only 57.9% of the median for males — a figure actually six points lower than had been achieved in 1955. Other data point in the same direction. The disparity is likely to be exacerbated for the widow. While the widower can usually continue in the occupation which preceded his spouse’s death, in many cases the widow will find herself suddenly forced into a job market with which she is unfamiliar, and in which, because of her former economic dependency, she will have fewer skills to offer.”
Justice DOUGLAS went on to uphold the statute, despite the gender based discrimination, because “. . . ‘the discrimination is founded upon a reasonable distinction, or difference in state policy.’ ” Kahn v. Shevin, supra, 416 U.S. at 354. The Stromsted rule is an effort to deal with the same kinds of problems faced by women that Justice DOUGLAS identified in Kahn. Given the current economic status of wives, we feel that this rule is the most equitable way to divide the liability between husband and wife for the family’s necessary expenses. It is important that the necessaries doctrine is a common law rule which has the ability to change over time to accord with changing societal needs and expectations. In the future it may be that wives will achieve greater equality with their husbands in terms of their relative financial strength. If that occurs then this rule may need to be modified, but for the present it is well suited to the relative economic status of the typical husband and wife.
*517By the Court. — Reversed and remanded to the circuit court for further proceedings not inconsistent with this opinion.
Because of the limited facts available in the record, we do not express an opinion as to whether an implied agreement, if any, can be construed as an express contract in this case.
Wengler v. Druggists Mutual Ins. Co., 446 U.S. 142, 150 (1980); Califano v. Westcott, 443 U.S. 76, 85 (1979); Orr v. Orr, 440 U.S. 268, 279 (1979); Califano v. Webster, 430 U.S. 313, 316-17 (1977); Craig v. Boren, 429 U.S. 190, 197 (1976).
“Marital and family patterns of the labor force,” Monthly Labor Review, October 1981, p. 36.
“Changes in marital and family characteristics of workers, 1970-1978,” Monthly Labor Review, April 1979, p. 50.
Ibid.
“Working wives’ contribution to family income in 1977,” Monthly Labor Review, October 1979, pp. 62-63.
“Occupational segregation and earnings differences by sex,” Monthly Labor Review, January 1981, p. 49.
See fn. 4, p. 50.
See fn. 3, p. 37.
Jersey Shore, Etc., v. Estate of Baum, 84 N.J. 137, 417 A.2d 1003 (1980), citing Weinberger v. Wiesenfeld, 420 U.S. 637, 645 (1975).