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Introduction and Background Information:
For our student generated lab our group decided to do a project that some might consider a bit abstract. Who really considers what factors play a role in the increasing population anyway? Well, after having sifted through work from like-minded persons, we have found that there are quite a few. Most reports seem to focus only on sexually transmitted diseases and birth control as factors in changing birthrates. These seem to be the same researchers who are concerned primarily with percentage or teenage mothers. Some articles focus on factors much more closely related to our hypothesis, effects of climate and other more natural changes, but most of these are not pecific to the United States, as our project will be. Still other studies attribute any changes in birthrate over time to education, money, or age of mothers. Some studies are from other countries or many different regions, which gives us an idea about how different regions consider factors of birth rate. With so many factors to consider, it is necessary for us, as it was for our fellow researches, to narrow down their field of vision. This explains the numerous differing projects concerning population.
Most people would agree that the growing number of teen pregnancy and sexually transmitted diseases is a serious problem. Much of our research was concerned with this matter, but we are happy to report that according to, "Understanding U.S. Fertility: Continuity and Change in the National Survey of Family Growth" by William D. Mosher, "concern with the AIDS epidemic led to increases in condom use between 1982 and 1990." Even teen pregnancy rates were falling during the 90's, as stated in, "U.S. Births Rise for First Time in Eight Years; Births to Teenagers Still Falling," by B. Brown. And of the pregnancies that remained were told that they were healthier, overall, US Birthrates Continued to Fall in 1993 "Including Rates Among Adolescents," from The Alan Guttmacher Institute, says "The birthrates for teenagers and for women in their 20s declined, while the birthrates for women in their 30s increased. While overall nonmarital fertility remained constant, rates declined among black women and rose among white women. Several factors related to healthy birth outcomes showed improvement in 1993 --the degree of tobacco use among pregnant women and the proportion of women utilizing prenatal care -- while others deteriorated -- the percentage of babies born preterm and at low birth weight." Which leads us into factors of race and age.
Race, age, wealth, education, and income are all considered factors in birthrates by the articles we researched. With regards to age, the studies show that there is a rise in the average age of first-time mothers, which is the topic of these and many other articles, "Among Women Over 30, Rate of First Births Rose Strongly with Education", by P. Rind and "Recent U.S. Fertility Patterns Continue: Birthrates Climb Among Older Women, Childlessness Rises" (in Digest) and "More U.S. Women are Deferring First Birth Till Their Mid- or Late 30s" (in digest). This may be because of the trend of later marriages according to, "The U.S. Fertility Decline, 1961-1975: The Contribution of Changes in Marital Status and Marital Fertility" by Campbell Gibson. Whether or not the mother can support her child should obviously be a factor, as addressed by Lee-Jay Cho in, "Income and Differentials in Current Fertility." "[W]omen in the labor force are less fertile than women not in the labor force, the author finds three differentials in fertility by income. This paper demonstrates, then, that the traditional inverse relationship between income and birth rates no longer holds among whites, and that even among Negroes, the previously well-established inverse relationship seems to be heading toward some modification. Finally, fertility differences for both whites and Negroes are smaller in urban than in rural areas," says Cho, also addressing the issue of race.
Some of the only articles that seemed to address the issue of climate as a factor on birthrate were mostly centered on a global scale. Few articles focused on United States. However, many included specific regions, "Low Fertility in Europe: A Report from the 1981 IUSSP Meeting" (in Special Report), by Deirdre Wulf, "Mexico's Experience Shows That Economic and Social Development Do Not Automatically Result in Slowing Rapid Population Growth," (in Digest), "Seasonal Variation in Conception in Rural Uganda and Mexico," by Richard W. Thompson; Michael C. Robbins, and "Half of Nicaraguan Women Use Contraceptives, Yet Birthrates Remain High," by L. Remez, which allows us a view of the wide-spread use of contraceptives and their effectiveness. Some researches chose to focus on a wide-spread or global scale, focusing sometimes on a few different areas at once. The articles, "The Ingredients of Recent Fertility Decline in Developing Countries," by Phillips Cutright, "Public Health Consequences of Global Climate Change in the United States-- Some Regions May Suffer Disproportionately, "by Janice Longstreth which states that, "seven possible (health effects that might increase worldwide with global climate change): heat stress, insect- and animal-borne disease, respiratory disease, allergic disease related to environmental allergens, developmental effects, i.e., perinatal mortality and/or preterm birth, health problems due to malnutrition and lack of water, and health problems due to crowding," "Tropical Acclimatization," but J. Elbert Cutler, and obviously, "World Population," by Warren D. Smith. There were a few articles, such as "The U.S. Birthrate," by June Sklar; Beth Berkov; Campbell Gibson, which chose to focus specifically on the factors of birthrates in only the United States, much like we intend to do with our own study.
We can see from our research that our study may, in fact, be one of a kind, but have decided not to let this discourage us. After all, we cannot really discover something that someone else has already found.
Question:
Is there a reason some cities have higher birthrates then others? Can a correlation be drawn between birthrate and issues related to the environment? Our group originally wondered if starry nights had higher conception rates verses clear nights and then we wondered if people who lived in warmer environments were more likely to have higher rates. We thought that it might have to do with people being happier in warmer sunnier climates. These questions interested our group and we wanted to find out if we could determine if climate played in birthrate. For our research we wanted to study the possible effect of birthrate in American cities only. We were interested in finding out if we could draw any correlations between birthrate and climate. We realized that there would be many different factors that play a key in the birthrate numbers. To try and best control our samples we will use cities with similar populations. Things like the percentage of women in the workforce, demographic statistics, and other similar issues will come into play but we will attempt like to focus on the factors related to the environment more. We feel that we can create a study that will attempt to focus in on environmental issues that affect the birthrate as much as possible. Factors such as the temperature and the number of cloudy days in the year 2000.
Hypothesis:
Our prediction is that areas with warmer temperatures, less rain and more cloudless days will have a significant effect on the birthrate in the area.
Methods:
"Who Procreates Where" is a study with many variables. Our group wishes to focus and emphasize the significance of climate on the birthrates in the U.S. To do this we will use data from the 2000 US Census at www.census.gov and facts about specific states in the year 2000 from www.city-data.com/city and information from the state departments of health and human services. The data on these sites should be significant to conduct our study.
The cities we will be using all have a population between 250,000 and 500,000, so that will not be a variable in out study. Other factors that we identified are: percentage of females in the population, percentage of the population that is white, median household income, percentage of the population with high school educations, average temperature, the total precipitation, the total days without clouds, and the total days with clouds.
Originally, we were going to study twenty-five cities. Due to difficulty in finding the birthrate data, we reduced our research to twelve cities.
The cities being studied are: 1)Fayetteville, North Carolina 2)Salem, Oregon 3)Trenton, New Jersey 4)Reno, Nevada 5)Lincoln, Nebraska 6)Corpus Christi, Texas 7)Spokane, Washington 8)Madison, Wisconsin 9)Jackson, Mississippi 10)Tallahassee, Florida 11)Rockford, Illinois 12)South Bend, Indiana.
After the data collection we will used Statview to analyze the data. The methods we used were Correlation Matrix and Fisher's r to z. The Correlation Matrix output the r-value. The r-value was then used to find the p-value to determine the significance of the data.
Results
Once our data was compiled and then entered into the Statview program, and found that our results failed to reject the null hypothesis. The most important information we were able to gather was from a correlation matrix.
Picture of Correlation Matrix
Picture of Fisher's r to z
By comparing the birthrate from each city to the cityÕs total population, percentage of females, median household income, percentage of white or Caucasian people, percentage of people with a high school education or higher, the average temperature, total precipitation days with clouds and days clear of clouds of the city for the year 2000, we were able to find some interesting correlation coefficients, r-values. When these r-values are squared they show us the percentage of how much difference can be considered chance. Our main concern on this chart is the column comparing Total Births to the other data. When compared to population, percent female, income, percent white, and education data, birthrate shows positive correlations. Perhaps the most notable of these results is the column comparing Total Births to the Median Household Income of each city. The r-values for this column show that the Median Household Income, though not technically significant, percentage of difference due to chance has an r-value of .507, which is only approximately twenty-five percent. In other words, almost seventy-five percent of the correlation between income and birthrate (the higher the income, the more births) is not due to chance. Education and Race, also positive numbers? The data pertaining to whether on the other hand, shows negative correlations to birthrate. The Average Temperature, Total Precipitation, Days With/Without Clouds seem to have no affect what-so-ever on birthrate. Conclusion notes Need more sources to have sig. data, but data difficult to find. High income equals high births, only in America
Conclusion:
"Who Procreates Where" was a study to determine what effects birthrate. Our p-value showed that our data was not very significant. The factors that were related to weather had negative r-values, meaning that we failed to reject the null hypothesis. The factor that had the most relevance to birthrate was the median household income. However, even income did not have a p-value that showed it was significant.
Even though our data isn't significant, the results point to a few conclusions. The data points to higher income families having higher birthrates. This is unusual because most often in America and around the world the opposite is true.
There were a lot of possible errors with our experimentation. The most obvious being the lack of data on birthrates for cities, thus the low number of cities sampled. If we had collected data on many cities we would have been able to determine more substantial effects on birthrate.
Our Day:
Our day is going to be a day of fun and shame. All I can say is condoms and bananas.
Works Cited
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Brown, B. "U.S. Births Rise for First Time in Eight Years; Births to Teenagers Still Falling." Family Planning Perspectives, Vol. 32, No. 5. (Sep. - Oct., 2000), pp.263-264. Stable URL:
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"Recent U.S. Fertility Patterns Continue: Birthrates Climb Among Older Women, Childlessness Rises." Family Planning Perspectives, Vol. 20, No. 1. (Jan. -Feb., 1988), pp. 44-45. Stable URL:
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Remez, L. "Half of Nicaraguan Women Use Contraceptives, Yet Birthrates Remain High." International Family Planning Perspectives, Vol. 20, No. 3. (Sep.,1994), pp. 116-117. Stable URL:
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