Jerome Lemelson, the independent inventor who founded the Lemelson Center, was concerned with the public profile of invention in the United States. Ask a young person to name 5 rock stars or superstar athletes, he'd often say, and you will get a full and immediate response. Ask that same teenager to name 5 inventors, and it's likely he or she would get stuck after coming up with Thomas Edison. How likely, then, is it that any American of any age could rattle off the names of 5 women inventors? Yet, the history of women inventors is as long as that of their male counterparts.
Sybilla Masters, for example, is often named as the first woman inventor in the American colonies. In 1715, the English courts awarded a patent--albeit, to her husband Thomas--for a method of making cornmeal from maize--"a new invention," the patent clearly stated, "found out by Sybilla his wife." [1]
She was not unique; the following century boasted many women inventors. For example, Mary Kies earned a patent--in her own name--in 1809 for a way of weaving straw that was put to use in the New England hat manufacturing trade.[2] Martha Coston perfected her husband's idea for colored signal flares after his early death. Coston not only patented the flare system, used by the navy in the Civil War, but also sold the rights to the government for $20,000 and earned a contract to manufacture the flares. [3] Margaret Knight's many inventions included a machine for making square-bottomed paper bags; her original patent is dated November 15, 1870. Think about that the next time the clerk at the grocery store asks, "Paper or plastic?"
Still, by 1910, inventions by women accounted for less than 1% of all patents issued in the United States. Why?
The answer lies, in part, in women's position in the social order. During the 19th century, the idea that "a woman's place is in the home" prevailed. Society's view of women's role limited their opportunities for a technical education or career, while laws in most states prohibited married women from owning property in their own names. Without training or independent funds, women often had to rely on husbands to make it through the expensive business of patenting an invention--a process that included costs for model makers, draftsmen for patent drawings, patent attorneys, and the fees charged by the patent office itself. While thousands of women inventors did successfully jump these hurdles, we can only assume that thousands more, like Sybilla Masters, saw her invention patented under a man's name, or perhaps under her own, represented only by her initials. Some women saw these options as the best way to market their inventions, knowing that prejudices against women's intellectual capabilities might thwart their work before it got into production.
Historians have looked at women inventors in the nineteenth century as a group distinct from their male counterparts. In doing so, they have examined deterrents to invention by women, the socioeconomic backgrounds of women inventors, the types and numbers of inventions, and the extent of women's involvement in invention and its consequences. These arguments fall into three broad categories: legal, economic, and social.
The legal rights of married women in the early-nineteenth century were virtually non-existent. As Grace Abbott, writing in 1932, unequivocally stated, "Under the common law, upon marriage a woman lost her rights, her responsibility, and even her identity." [4] A number of historians point to married women's inability to control their own property as both a deterrent to invention by women and a loophole through which women's inventions slip when patents for women's inventions were issued to men. [5] Matilda Joslyn Gage, writing in 1883, passionately described the dilemma of women inventors.
In not a single State of the Union is a married woman held to possess a right to her earnings within the family; and in not one-half of them has she a right to their control in business entered upon outside of the household. Should such a woman be successful in obtaining a patent, what then? Would she be free to do as she pleased with it? Not at all. She would hold no right, title, or power over this work of her own brain. She would possess no legal right to contract, or to license any one to use her invention. Neither, should her right be infringed, could she sue the offender. Her husband could take out the patent in his own name, sell her invention for his own sole benefit, give it away if he so chose, or refrain from using it, and for all this she would have no remedy. [6]
The number of patents issued to women did increase beginning with changes in property-rights laws mid-century. [7] Beyond the women represented on the patent rolls, however, are scores and scores who never undertook the formal process of patenting an invention. These women are very difficult to document and, unfortunately, many of their stories are lost to us.
As the 19th century continued, prospects for women inventors--and, indeed, women in general--did brighten. In addition to legislation that changed women's status as property holders, the women's rights movement coalesced at the Seneca Falls Convention in 1848 and sought equality in educational opportunities, voting and property rights, and in society as a whole. Even the Civil War played a role in extending women's sphere. Rosie the Riveter's grandmother was inventing machinery for farms and factories while her male relatives were off fighting. World's fairs provided publicity for inventions by women. The 1876 Centennial Exposition in Philadelphia and the 1893 Columbian Exposition in Chicago both had women's buildings that featured exhibitions of inventions by women.
While legal status may have deterred or obscured inventions by women, economic considerations fostered it. Both a perceived market need and the opportunity for economic gain factor in an inventor's motivation. In writing about the women inventors who participated in the 1876 Centennial Exhibition in Philadelphia, Deborah Jean Warner pointed out that a quarter of them were unmarried or widowed; for these women, a successful invention promised economic security. [8] Warner summarized her argument by stating that "to make money is mainly what the women inventors at the Centennial were trying to do." [9] There were, of course, exceptions within the community of women inventors, perhaps most notably, the women inventors in the Shaker community. The Shakers' communal, non-capitalistic system spurned the monopoly granted by patents. Without patent records, the names, numbers, and success rates of Shaker inventors, both male and female, and their inventions cannot be measured accurately. [10]
Many women inventors, however, were successful financially. Warner stated that 75% of the patents issued to women between 1895 and 1900 were turning a profit. [11] Olive Gunby, writing for the Scientific American Supplement in 1901, agreed: "Men acquainted with the field say that fully one hundred of the patents taken out by women within the past five years are yielding unusually large returns to the inventors, and that others not yet put on the market are destined to be equally successful." [12]
Gunby also attempts to categorize both the inventors and their inventions. These statements lead into the third area of historical discussion on women inventors, namely, the definition of the status of the woman inventor within society. Gunby notes that few southern women received patents and that women tended to invent in the areas that they knew best: "It is noticeable that the women inventors registered from the larger cities of the country have almost invariably patented articles pertaining to the elegancies of dress and household furnishing, while inventive faculty in the country districts and villages has been directed to conveniences and labor-saving devices in similar lines. "[13] She cites examples of office inventions by urban women, agricultural inventions by rural women, educational inventions by schoolteachers, and factory inventions by women in mill towns. Fred Amram agrees that experience is a prime motivation for invention: "If a creative woman's horizons are bounded by the household or the farmstead, then she will invent domestic or agricultural implements." [14] The Shaker belief in simplicity and a balanced life similarly encouraged invention to eliminate unnecessary drudgery in daily chores. [15]
Some historians, however, note a change in both the number and types of inventions between the antebellum and post-Civil War periods. Ethlie Ann Vare and Greg Ptacek found that overall "a preponderance of inventions by women pertain to household maintenance," but that "the world by the 1870s had had its fill of foldable beds, desks, rocking chairs, tables and bathtubs, then the mainstays of distaff inventiveness." [16] Gunby offered another reason for diversification in inventions by women when she looked at women's exposure to traditionally-male tasks as men went off to fight in the Civil War. [17] All of these historians agree that increased educational opportunities for women in the second half of the nineteenth century were another important factor in the rise in number of inventions by women. [18]
Some statistics illustrate this rise in inventive activity. In the decade between 1855 and 1865, patents issued to women increased 676.9% over those issued during the previous ten years. Similarly, patents issued during 1865-1875 show an increase of 566.3% over the previous decade. However, these dramatic figures come into perspective when compared with men's totals. During 1855-1865, women received an annual average of 10.1 patents, which increased to 67.3 during 1865-1875. For the same periods, men received an annual average of 3,767.4 and 11,918.4 patents, respectively. [19] It is difficult to consider women inventors a significant force in the history of technology when, as Amram states, "by 1910 the number of women's patents was still only 8596, just 0.8 per cent of the total." [20]
Considering these legal and economic factors affecting women inventors, what general conclusions can we draw about their social status? These women seem to be defined more by economics than geography. The south was not heavily represented, but the majority of women inventors from that and other areas of the country, whether rural or urban, belonged to white, middle-class society. The literature I've referred to in this paper contained only a single reference to an African American woman inventor, one who sold her clothes-wringer patent for $18 because she feared "white ladies" would not buy her product if they learned of her race. [21] As further evidence of the predominance of white, middle-class women, Warner noted a growing support of the suffrage and other reform movements. She claims that these beliefs influenced the women's inventions and their decision to exhibit their work in the Women's Pavilion, rather than in other halls at the Centennial Exhibition. [22] Finally, Warner describes the appeals to women that regularly appeared in Scientific American that assured them "that there [was] nothing inherently unladylike about the process of invention. Like novel writing, it could be done in the parlor at home, and did not require traffic in the factory or marketplace." [23] Obviously, such statements were not aimed at the working class woman.
So historians have given us a picture of women inventors in the 19th century as a group that faced and often overcame significant hurdles to achieve their goals. As we rapidly approach the end of the 20th century, how much has this characterization changed? Much of the history of contemporary women inventors remains to be written, but I'd like to share the personal stories of just a few of the women who have stepped through the doors opened by their counterparts a century ago. I hope it will give you an idea of the growing diversity found in the community of women inventors over the course of the 20th century, as well as the continuing challenges these women face.
Beulah Henry began sketching out inventions when she was a young girl. In 1912, at age 25, she received her first patent, for an ice cream freezer. A year later, she patented a handbag and a parasol. By 1924, she could claim, "I have my inventions patented in four different countries and I am President of two newly incorporated companies." [24] In all, Henry earned 49 patents, the last one issued in 1970.
But for someone with such a long inventive career, surprisingly little is known about Beulah Henry's personal life. A descendant of Patrick Henry, she was born in Raleigh, North Carolina, in 1887 and grew up in an artistic family--her father was an authority on art, her mother, an artist, and her brother, a songwriter. She entered university in 1909, attending Presbyterian and Elizabeth Colleges in Charlotte, North Carolina. We assume that she received a liberal arts education, since she was always honest about her lack of technical and mechanical skills. "I cannot make up my mind," she said, "whether it is a drawback or an advantage to be so utterly ignorant of mechanics as I am. I know nothing about mechanical terms and I am afraid I do make it rather difficult for the draughtsmen to whom I explain my ideas, but in the factories where I am known they are exceedingly patient with me because they seem to have a lot of faith in my inventions." [25]
It seems she never married and lived in hotels throughout her life, spending many years, from the 1920s on, in New York City. She employed mechanics, model makers, and draftsmen to turn her descriptions of inventions into working prototypes. Models of her patented inventions filled her Hotel Victoria rooms in New York.
Outside the workshop, her memberships in organizations like the Museum of Natural History, the Audubon Society, and the League for Animals hint at a love of nature and wildlife. Articles in the popular press referred to her "superb auburn hair" and "commanding presence." [26] Reporters commented on her feminine grace, one writing that she looked "more like Mae West than the movie conception of an inventor" [27] (whatever that conception might be!). And her upbringing among artists was reflected in her own paintings and in her desire to be a writer. She told one reporter, "I think literature and art are far above things mechanical. I have . . . painted many water colors, but the world calls me an inventor." [28] And it is by her inventions that we remember Henry today. Their diversity and number are still impressive.
One of her most successful inventions was an umbrella with changeable, snap-on covers. The idea was that a woman could easily coordinate her parasol with her outfit. But figuring out how to attach the covers--and have them stand up to windy days--was quite tricky. In fact, as Henry herself put it, "The biggest umbrella men in the country said it could not be done." [29] She added, "Of course, I did not believe them." She invented a process that earned her about $50,000 from the manufacturer and saw her umbrellas showcased in the windows of Lord and Taylor's. [30]
Another "snapping" invention was the "Latho"--a sponge that opened to hold a bar of soap and then snapped closed to keep it inside. It not only combined washcloth and soap, but floated. But again, manufacturing the invention was a problem. Henry couldn't find a machine to cut the sponges correctly. So she designed one. For younger bathers, the "Latho" came in the shape of dolls.
Henry created a number of educational inventions for children, including a "Kiddie Klock" to teach time-telling and a board game called "Cross Country." Basically, players had to traverse the country along the major railroad routes, without running into another player (which would automatically send them back to their station of departure). In the course of their journeys, they learned about the geography of the country and how to navigate it by train.
One more toy, the "Miss Illusion" doll, will close this brief look at Beulah Henry's career. "Miss Illusion" had interchangeable wigs, blonde and brunette. At the push of a button, her eyes could turn from blue to brown. Her dress was reversible. And a mechanism inside her closed her eyes.
When a reporter asked Beulah Henry why she was an inventor, she replied, "I invent because I cannot help it." [31] Her fertile imagination made her one of the most prolific women inventors of the early 20th century and earned her the nickname, "The Lady Edison."
In 1913, a year after Beulah Henry received her first patent, Hedwig Eva Maria Kiesler was born in Vienna, Austria. At age 17, she made her first film, titled "Money on the Street." Two years later, she earned notoriety for her nude romp through the woods in the Czech film, "Ecstasy." She married a rich Austrian munitions dealer named Fritz Mandl and was party to his meetings on arms design. Her inventive streak surfaced in suggestions for a radio-controlled torpedo.
When Austria fell to Germany in 1938, Hedwig left her husband and her country and went to London. There, she met Louis B. Mayer, who signed her for MGM and, along with a new life, gave her a new name--Hedy Lamarr. In 1939, she remarried, this time to writer Gene Markey.
While making films like "Algiers," "White Cargo," and "Tortilla Flats," kept the actress busy, the inventor in her was anxious to help the war effort. She revived her radio-controlled torpedo idea in conversations with composer George Antheil and the two of them came up with a plan to use frequency hopping to prevent jamming the signals sent to guide the torpedo. Frequency hopping basically means changing the frequency of a radio signal rapidly and randomly, something like what happens when you hit the "scan" button on a car radio. The unpredictable changes would make it impossible to intercept the torpedo or change its course.
The way the composer and the actress proposed doing this drew on their experience in the arts, especially on Antheil's work in electronics and music. In the 1920s, he had composed a piece called Ballet Mécanique that incorporated synchronized player pianos. He believed he could adapt this concept to Lamarr's idea of frequency hopping. The transmitter they sketched out used slotted-paper rolls, like those of a player piano, to send a pattern of 88 (the number of keys on a piano) changing frequencies. The receiver, mounted on the torpedo, would have a duplicate slotted-paper roll, so it would only recognize signals that matched those sent by the transmitter. They applied for their patent six months before the United States entered the war, and received it in August 1942.
The system was not used by the military during the war, but after Lamarr's patent expired, electronics were substituted for the paper rolls and the concept of frequency hopping is used in anti-jamming technology today. Remembered more for her beauty than for her brains, Hedy Lamarr, inventor, once quipped, "Any girl can be glamorous. All you have to do is stand still and look stupid." [32]
While Hedy Lamarr hoped her invention would speed the end of the war, her contemporary, Bessie Blount, invented a way to help those who had suffered grave injuries in the fighting. Blount, an African American, was born in Hickory, Virginia, around 1914. Details of her life are sketchy, but we know she traveled north and studied at Union Junior College and the Panzer College of Physical Education, both in New Jersey, and furthered her training as a physical therapist in Chicago. Working in veterans' hospitals with soldiers who had lost their arms, she began to think about ways to give them more independence. She taught some of her patients to do with their feet some of the things they used to do with their hands--like typing to replace handwriting. At the suggestion of a doctor, she began to design something that would let amputees feed themselves.
She conceived of an electrical apparatus that would deliver food through a tube, one bite at a time, to a mouthpiece that could be used whether the patient were sitting or lying down. Biting down on a switch would signal the machine to send the next mouthful. At this point, the story gets a bit fuzzy. In 1948, Blount (under the name Bessie Griffin) applied for a patent for a "portable receptacle support" which did indeed allow people without arms to feed themselves. But this was a much simpler system that used a brace around the neck to support a bowl, dish, or cup. She received her patent in 1951.
By that time, Blount had settled in Newark, New Jersey. She was a practicing physical therapist and a teacher of the subject at Bronx Hospital in New York. She tried, without success, to get the Veterans Administration to adopt her invention. She tried to sell the feeder herself. She ended up signing over the rights to the French Government in 1952, stating that she had proved "that a black woman can invent something for the benefit of humankind." [33]
Bessie Blount sought to make life a bit better for those who had suffered traumatic injuries. Stephanie Kwolek's inventions helped save lives and prevent injuries. Just ask any law enforcement officer whose life was spared, thanks to a bullet-resistant Kevlar vest.
Stephanie Kwolek was born in 1923 in New Kensington, Pennsylvania. She had a penchant as a child for exploring the natural world with her father, collecting wildflowers and seeds for her scrapbook. She also developed an interest in technology by making clothes. "When I was six," she recalled, "I loved to use my mother's sewing machine. I was forbidden to use the sewing machine, but I would sneak in when my mother went shopping." [34]
In 1942, Kwolek enrolled at the Carnegie Institute of Technology (now Carnegie-Mellon University). She majored in chemistry and minored in biology, hoping to enter medical school after earning her bachelor's degree. With that in mind, she took a job at DuPont to build savings for her further education. She never carried out that plan, though.
"When I joined DuPont in 1946," Kwolek remarked, "women were having a very difficult time in science. Women who got jobs in the lab would stay only a few years; they were encouraged to move into so-called 'women's fields.' They were not promoted as rapidly as the men--women I know, even Ph.D. women, lasted about two or three years, and then went back to teaching, frequently at a women's college. But there were some of us who decided to stick it out, and I was one."
Kwolek's work focused on polymers, the long, chain molecules at the base of synthetic fibers like nylon. She concentrated on finding polymers that would dissolve at low heat so they could be spun into fibers at room temperature. When she was assigned to research extra strong and stable polymers in 1964, she turned to liquid crystal solutions in which all the molecules line up in one direction--like a string of pearls, as she often described it. Her experiments yielded a solution unlike any she'd ever seen. While most polymer solutions were thick and clear, like syrup, this was thin and hazy-looking. Its milky texture made the technician nervous about putting the solution into the fiber-making machine, called a spinneret. He thought there probably were solid particles that would clog up the spinneret's fine holes. But Kwolek convinced him that the solution was safe to spin, and the resulting fibers were exceptionally strong--much stronger than steel, in fact.
Today, Kevlar is found in a range of products, from bullet-resistant vests to ropes that anchor oil rigs to the ocean floor to skis. And Stephanie Kwolek, who retired in 1986 with 17 patents to her name and was inducted into the National Inventors Hall of Fame in 1995, doesn't regret not making it to medical school. "Most chemists," she said, "work all their lives . . . and are never able to participate in a discovery that has done so much good as Kevlar."
Just beginning what promises to be a rewarding career as an inventor is Jeanie Low of Houston, Texas. A teenager now, Jeanie received U.S. Patent No. 5,094,515 in 1992 for her invention of the "Kiddie Stool." Frustrated at not being able to reach the bathroom sink and spurred on when the plastic stool she used broke, Jeanie decided to craft a folding stool that would be hinged to the vanity under the sink.
"My parents took me to a building supply store," she explained. "I picked out some wood, and I told the man at the store how I wanted him to cut the wood and what it was for. He said it would not work." [35] Needless to say, that man was wrong.
As women have attacked stereotype after stereotype during this century, so have women inventors defied type casting. Their one common bond is an innate curiosity that spurs them on to find something new, something better. Women inventors still have a tough road ahead of them. Today, only about 10% of all patents are awarded to women. [36] Hopefully, as we learn more about these creative women, their stories will inspire future generations of "Lady Edisons."
This paper was originally presented at a Lemelson Center teachers' workshop in July 1999.
For further reading:
Anne L. Macdonald, Feminine Ingenuity: How Women Inventors Changed America (New York: Ballantine Books, 1992).
Autumn Stanley, Mothers and Daughters of Invention: Notes for a Revised History of Technology (Metuchen, NJ: Scarecrow Press, 1993).
Martha Moore Trescott, ed., Dynamos and Virgins Revisited: Women and Technological Change in History (Metuchen, NJ: Scarecrow Press, 1979).
Ethlie Ann Vare and Greg Ptacek, Mothers of Invention: From the Bra to the Bomb, Forgotten Women and Their Unforgettable Ideas (New York: William Morrow and Co., 1987)
Ethlie Ann Vare and Greg Ptacek, Women Inventors and Their Discoveries (Minneapolis: Oliver Press, Inc., 1993).
For younger readers:
Women Inventors, Cobblestone Magazine, vol. 15, no. 6 (June 1994).
Frances A. Karnes and Suzanne M. Bean, Girls and Young Women Inventing (Minneapolis: Free Spirit Publishing, 1995).
Ellen H. Showell and Fred M.B. Amram, From Indian Corn to Outer Space: Women Invent in America (Peterborough, NH: Cobblestone Publishing, Inc., 1995).
Annie Wood, Canadian Women Invent! (Toronto, Ontario: Inventive Women Inc., 2002).
Footnotes:
1 Ellen H. Showell and Fred M.B. Amram, From Indian Corn to Outer Space: Women Invent in America (Peterborough, N.H.: Cobblestone Publishing, 1995), pp. 58-61; and Ethlie Ann Vare and Greg Ptacek, Women Inventors and Their Discoveries (Minneapolis: Oliver Press, Inc., 1993), p. 10.
2 Ibid., p. 12.
3 Ibid., p. 23; Anne L. Macdonald, Feminine Ingenuity: Women and Invention in America (New York: Ballantine Books, 1992), pp. 16-19, 49-50, 93, 182.
4 Abbott, Grace, "The Changing Position of Women." In A Century of Progress, edited by Charles A. Beard, p. 257 (New York: Harper and Brothers Publishers, 1932).
5 Pursell, Carroll. "Women Inventors in America." Technology and Culture 22, no. 3 (July 1981): 546; Amram, Fred. "The Innovative Woman." New Scientist 102, no. 1411 (24 May 1984): 11.
6 Gage, Matilda Joslyn. "Woman as an Inventor." North American Review 136, no. 318 (May 1883): 488.
7 Warner, Deborah J., "Women Inventors at the Centennial." In Dynamos and Virgins Revisited: Women and Technological Change in History, edited by Martha Moore Trescott, p. 104. (Metuchen, NJ: Scarecrow Press, Inc., 1979.).
8 Warner, pp. 105-106.
9 Ibid., p. 108.
10 Irvin, Helen Diess, "The Machine in Utopia: Shaker Women and Technology." In Women, Technology and Innovation, edited by Joan Rothschild, p. 315. (New York: Pergamon Press, 1982.).
11 Warner, p. 104.
12 Gunby, Olive F. "Women Inventors." Scientific American Supplement 51, no. 1325 (25 May 1901): 21241.
13 Ibid.
14 Amram, p. 11.
15 Irvin, pp. 313-314.
16 Vare, Ethlie Ann, and Greg Ptacek. Mothers of Invention. (New York: William Morrow and Co., Inc., 1988): 37, 107.
17 Gunby, p. 21242.
18 Amram, p. 10; Gunby, p. 21242; Vare and Ptacek, p. 183.
19 Pursell, p. 547.
20 Amram, p. 10.
21 Pursell, p. 548.
22 Warner, pp. 107-108.
23 Ibid., p. 104.
24 "A Study in Feminine Invention." Scientific American 131, no. 4 (Oct. 1924): 260. For additional information on Beulah Henry, see Vare and Ptacek, pp. 199-200; Macdonald, pp. 295-297, 301, 308-309; and Autumn Stanley, Mothers and Daughters of Invention: Notes for a Revised History of Technology (Metuchen, N.J.: Scarecrow Press, 1993), pp. 611-619.
25 Ibid.
26 Stanley, p. 612.
27 Macdonald, p. 296.
28 Stanley, p. 613.
29 "A Study in Feminine Invention," p. 260.
30 Macdonald, p. 297.
31 Ibid., p. 296.
32 Macdonald, p. 319. For additional information on Hedy Lamarr, see David Kahn, "Cryptology and the Origins of Spread Spectrum," IEEE Spectrum 21, no. 9 (Sept. 1984): 70-80; Vare and Ptacek, pp. 230-232; Stanley, pp. 557-559, 898-899; and Richard L. Mattis, "Movie Star Inventor: Hedy Lamarr," in Cobblestone: Women Inventors 15, no. 6 (June 1994): 29-31.
33 Stanley, p. 258. See also U.S. Patent No. 2,550.554, issued 24 April 1951.
34 Interview with Stephanie Kwolek, conducted by the Lemelson Center for the Study of Invention and Innovation, National Museum of American History, Smithsonian Institution, Washington, D.C., 1996. For additional information on Kwolek, see Vare and Ptacek, pp. 192-193; Macdonald, pp. 373-375, 377; Showell and Amram, pp. 58-61; and Ethlie Ann Vare and Greg Ptacek, Women Inventors and Their Discoveries (Minneapolis: Oliver Press, Inc., 1993), pp. 137-147.
35 "The Youngest Female--Jeanie Low," National Inventive Thinkers Association Newsletter 6, no. 1 (Oct. 1994): 2. See also Richard L. Mattis, "The Youngest Female Inventor: Hedy Lamarr," in Cobblestone: Women Inventors 15, no. 6 (June 1994): 40-41.
36 Buttons to Biotech: U.S. Patenting By Women, 1977 to 1996 (Washington, D.C.: U.S. Dept. of Commerce, 1999), p. 9.