Chapter 3 Tracking the aids epidemic in the United States: Diffusion Through Space and Time A. Logistics



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Chapter 3
Tracking the AIDS Epidemic in the United States:

Diffusion Through Space and Time
A. Logistics
Students’ Time Requirements

Activity 1: Mapping the Diffusion of AIDS 30 minutes

Activity 2: AIDS Rates and Distance from Initial Centers 30 minutes

Activity 3: S-Curves 30 minutes


We recommend you do both Activities 1 and 2, because a key goal is to compare and contrast the two different diffusion processes. Activity 3 (on S-curves) is independent of the other two and is optional. One of the benefits of Activity 3 is the chance to focus on your local area.
All activities require access to the internet. They can be done individually or in groups, in a computer lab or outside of class. Students who work efficiently may be able to complete all three in an hour-and-fifteen-minute class.
B. Lesson Plan
I. Spatial Diffusion

  1. Diffusion defined.

  2. Diseases are not the only phenomena that spread through space and time. The concept also applies to cultural traits and innovations.

  3. Types of diffusion: Torsten Hägerstrand

    1. Relocation

    2. Expansion

    3. (The distinction between relocation and expansion diffusion keys on whether the number of adopters is expanding)

  4. Temporal regularities

    1. S-curve

      1. Innovators

      2. Majority adopters

      3. Laggards

    2. Adoption rate saturation level for different products

      1. Examples of different transportation technologies

  5. Spatial regularities in diffusion

    1. Contagious effects

    2. Hierarchical effects

i. Urban hierarchy

    1. Disentangling contagious and hierarchical diffusion. Usually both are at work in any situation.

    2. Barriers or facilitators of diffusion

      1. Physical

      2. Language

      3. Cultural

      4. Political

      5. Transportation

    3. Biased innovations

II. Examples of diffusion



  1. Cricket

  2. Cellular phones

  3. Hydrogen fuel stations

  4. Clothing fads

  5. Video games

  6. Radio broadcasting

  7. Punk rock, computers

  8. Chemical fertilizers for farming

  9. Anti-HIV drug “cocktail”



III. Background on AIDS

  1. What is AIDS?

    1. Acquired Immunodeficiency Syndrome

    2. Caused by HIV virus

    3. Mechanisms of transmission—not just via homosexual activity

    4. Recent medical advances

  2. AIDS in Africa

    1. Origin through zoonosis (disputed by some researchers)

    2. Very high rates in Africa

    3. Factors causing high rates in Africa

      1. Spread along trade and migration routes

      2. Heterosexual transmission

      3. Postcolonial development patterns causing migrant work, prostitution

      4. Poverty, famine, war are perceived as graver threats

      5. Ignorance and misinformation

    4. Devastating effects of AIDS in Africa

      1. Shortened life expectancies

      2. Attacks adults in their prime, increases dependency ratio

      3. Diverts resources from development needs

      4. Orphans

      5. Young women are hardest hit

    5. Ingredients of successful anti-AIDS policies

      1. Condoms and circumcision

      2. Treating infected persons

      3. Antiviral drugs for expectant mothers

      4. Female empowerment

  3. Global pathways and global hotspots

    1. Haiti

    2. New York, California, Miami

    3. Thailand

    4. Western and Eastern Europe

  4. Current situation in the United States

    1. Stabilizing rate of new infections

    2. Growing complacency due to new treatments

IV. Do Activities 1–3 in computer lab if available. Otherwise, assign as homework. Prepare your students by asking them beforehand what they would expect to see if AIDS spread predominantly by contagious diffusion? By hierarchical diffusion?


V. Discussion
C. Answer Key
1.1 (Note: highlighted answers changed from the .5e)


Year



Number of New Metro Areas Appearing on Map Within

the Top 15

Number of New Metro Areas Appearing on Map Not Within the Top 15


Total Number of New Metro Areas Appearing on the Map (add the two columns to the left)

1986

2

0

2


1987

1

0

1


1988

2

0

2


1989

2

1

3


1990


5


1


6

1991


4


4


8

1992


3


2

5


1993


8


11


19

1994

1



10


11

1995

2

9

11


1996

0

8

8


1997

1



7

8


1998

1

0

1


1999


0


2


2

2000

0

2

2


2001


0


1


1

2002

0

1

1


2003

0

0

0


2004

0

0

0


2005

1

1

2


2006

0

1

1


2007

1

0

1


2008

0

1

1


2009

0

0

0


2010

0

0

0



Note: As of 2003, the terms CMSAs and PMSAs no longer are used by the census (see Chapter 10 for explanation of new urban definitions), but we continue to use these terms in this chapter because the 1990 definitions of urban areas apply best to the time period of study.
Note: It is sometimes not clear whether the following cities appear in a Top 15 metro region because they lie near the CMSA boundary. You may want to be understanding if your students classify them incorrectly. You may want to advise your students that, if they are not sure if it’s in or not, to go to the following year when the black diamond will change to a smaller blue square, which may make it easier to determine which side of the boundary they are on.

1992 New Haven, Connecticut is within the New York CMSA

1993 Wilmington, Delaware is within the Philadelphia CMSA

1994 Providence, Rhode Island is not within the Boston CMSA

1996 Stockton, California is not within the San Francisco CMSA


  1. Gary, Indiana is within the Chicago CMSA.

2002 Toledo, Ohio, is not within the Detroit CMSA

2005 Akron, Ohio, is within the Cleveland CMSA

2006 Scranton, PA, is no within the New York CMSA

2007 Youngstown, Ohio, is within the Cleveland CMSA


Note: It could be confusing for some students that there are more than 15 places in the top 15 metro regions. It is important to explain to them that some CMSAs (metro regions) contain numerous PMSAs (metro areas). As of 2003, these are simply called Combined Statistical Areas (CSAs) and Metropolitan Statistical Areas (MSAs).
Note: The large number of cities passing the threshold in 1993 may be affected by these factors: (1) better reporting of AIDS; (2) a lowering in the standard of what officially constitutes an AIDS case; (3) larger number of cities at that population size; and (4) a cresting of the AIDS epidemic.
1.2 Yes, the table does provide evidence for hierarchical effects in the diffusion of AIDS. In general, metro areas in the Top 15 metro regions reached the threshold of 100 cases per 100,000 population earlier than those not in the Top 15. Specifically, students could make a strong case by saying that from 1986 to 1990, the ratio of Top 15 metro areas to non-Top 15 metro areas was 12:2, whereas from 1991 to 2010 it was 22:60.



1.3 Miami reached the threshold earlier than Seattle for several reasons. First of all, it is closer to Haiti, the source from which the AIDS virus first entered the United States. In fact, Miami serves as a hub for airlines and cruise ships to the Caribbean. Miami also has a larger than average gay population, a factor that is important because it was this population among which the disease first spread within United States.
1.4 San Francisco has a relatively high percentage gay population, an early population through which the disease spread. San Francisco also has more contact with outsiders through its role as a hub airport and tourist destination. More contact with individuals from outside an area increases the opportunity for the diffusion of a disease. AIDS is an example of biased innovation, in the sense that it’s not only where you live that determines your likelihood of contracting it, but also who you are and your social context.
1.5 AIDS seems not to spread into more remote areas such as the upper Rocky Mountain west. Areas with larger cities such as the Northeast, southern California, and finally the southeast have served as pathways for the disease. Note: some students may answer that the spread of AIDS has tended to follow along the coasts. This is a refection of the fact that many large cities in the U.S. are located near coasts.
1.6 Cities with less than a million people crossing the threshold of 100 cases per 100,000 population between 1986 and 1990 include: 1) West Palm Beach, Florida, and 2) New Orleans, Louisiana. Note: some students may answer New Haven, Connecticut, which appears to be on the boundary of the New York CMSA, but it is actually within the New York CMSA.


    1. West Palm Beach, although not technically within one of the 15 largest metro region boundaries, is nonetheless close to larger metropolitan areas which do lie in this category. In some ways, then, it is more likely to pass the threshold earlier than other mid-sized cities that are more isolated, because it is also being affected by contagious diffusion. New Orleans is a major tourist destination and so probably has more contact with the outside world (thus increasing contacts and possible exposure to the disease).


Note: A common student response here is that West Palm Beach is a major Spring Break destination. Students may be confusing West Palm Beach with Fort Lauderdale, or simply lumping all of South Florida together as a Spring Break destination.
2.1 The height of the curve increases over time. The AIDS rates for most of the metropolitan areas increases over the 25-year interval.
2.2 (a) In general, the farther a city is away from the initial center of diffusion of the AIDS virus the lower its rate of AIDS. (b) This distance decay curve does provide evidence of spatially contagious diffusion. (c) There is quite a bit of scatter, however, especially in the case of Miami.
2.3 Several things might account for outliers. If a city is larger than average, it might be feeling the effects of hierarchical diffusion as well as contagious diffusion. Large tourist destinations, with more contact with the outside world than otherwise expected, may also have a higher than expected rate of AIDS. Finally, religious or otherwise sexually conservative communities may prove to be more resistant to the spread of the disease than other cities.
A.

Year


Number of New Metro Areas

Added Each Year

Cumulative

Number of

Metro Areas

1986

2

2

1987

1

3

1988

2

5

1989

3

8

1990

6

14

1991

8

22

1992

5

27

1993

19

46

1994

11

57

1995

11

68

1996

8

76

1997

8

84

1998

1

85

1999

2

87

2000

2

89

2001

1

90

2002

1

91

2003

0

91

2004

0

91

2005

2

93

2006

1

94

2007

1

95

2008

1

96

2009

0

96

2010

0

96

B.


    1. 1990 is probably the best answer for explaining when the S-Curve passed from the innovator stage to the majority adopter stage.


Note: Remember that the large jump in AIDS apparent in this and the other S-Curves in 1993 is partly the result of a change in the government definition of AIDS.
Note: Remember also that “majority adopters” implies that the majority of those who eventually adopt or get infected do so in this stage, and not that the majority of ALL people adopt at this time.
3.2 It looks like the shift from majority adopter to laggard stage began in 1998 as that is when the largest slow-down occurs. Clearly a slower trend occurs after 1997. Post-2000 the trend is nearly flat.



3.3-3.4 Answers will vary depending on the city chosen by students for this question, but it should be backed up by a printout as per instructions.
Note: The sixth edition of this book added data for the years 2004 through 2010. The population estimates used in the fifth edition for the years 2001 through 2003 at times differ greatly from the values published after the 2010 Census. Also, some Metropolitan Area boundaries were revised in 2004. Students might notice a jump in 2004 for some cities as a result.
Note: New Orleans has a very strange jump in AIDS rates in 2006 as a result of Hurricane Katrina hitting in 2005. The base city population dropped dramatically, but apparently those with AIDS did not leave at the same rate as the general population, thereby elevating the values greatly. The numbers stabilize by 2007, but still at a higher rate than prior to Katrina.
3.5 (a) there are multiple good choices. Some would be:

West Palm Beach, FL; Riverside, CA; Wichita, KS; Seattle, WA; or Portland, OR; or San Francisco, CA

(b) Again, there are numerous good choices. Some would be:

New Orleans, LA (see note above); Providence, RI; Washington, DC; Syracuse, NY; or Sacramento, CA

(c) Among the good choices here might be:

Detroit, MI; Toledo, OH; St. Louis, MO; Baton Rouge, LA; Omaha, NE; or Dayton, OH


D. Discussion or Essay Questions

What is the newest, coolest trend among college students today? Where did it originate? How did it get here? How long did it take? What percent have adopted it already?


What did you learn in this exercise that would help you in marketing athletic shoes or a new cell phone app?

Can you think of anything that you adopted very early in the S-curve? Anything in which you were a late adopter or non-adopter?


Have we manipulated your impressions of the diffusion of AIDS through our selective choice to map AIDS rates in metropolitan areas?
Does the diffusion of AIDS in the U.S. follow an S-curve pattern?
Why do you suppose New York, Miami, and LA/SF were early epicenters of AIDS?
On the Miami scatterplot, what reasons other than population contribute to Dallas being an outlier above the line?
Would other diseases diffuse according to the same time-space pattern as AIDS?
How do you suppose AIDS would have spread 150 years ago?
Name some other phenomena that diffuse hierarchically?
Name some other phenomena that diffuse contagiously?
What characteristics determine whether a phenomenon will diffuse hierarchically or contagiously?
Do you see any evidence for relocation diffusion in the spread of AIDS? If not, what data would be necessary to test for relocation diffusion?
If you were a marketing manager for a company (e.g., an athletic shoe company or a music label), how could you apply your knowledge of spatial diffusion?
What other professions besides marketing and disease control might benefit from knowledge of diffusion?
Have recent medical advances in the treatment of HIV/AIDS changed your perception of the disease, or your personal behavior?
How have recent communication technologies like the internet and social media networks affected the diffusion of phenomenon?
What technologies do you think might be in the Early Adopter stage of diffusion?
E. Question Bank
1. True/False The diffusion of AIDS in the United States in the late-1980s is mainly an example of relocation diffusion.
2. True/False The westward spread of the American frontier is an example of relocation diffusion.
3. True/False In its earliest stages, punk rock diffused hierarchically.
4. True/False Expansion diffusion refers exclusively to things that spread like a wave through geographic space.
5. True/False The individuals who first adopt a new innovation or idea, or catch a disease, are represented at the bottom of the S-curve.
6. True/False AIDS is spread through contagious diffusion, not hierarchical diffusion, because it requires direct personal contact for contracting it.
7. True/False Expansion diffusion can have both contagious and hierarchical effects.
8. True/False In Africa, the AIDS virus is more prevalent among the homosexual population than the heterosexual population.



9. True/False A Consolidated Metropolitan Statistical Area (CMSA) includes two or more Primary Metropolitan Statistical Areas (PMSA).
10. True/False Contagious diffusion can only describe the spread of a disease, not an idea.
11. True/False It is not possible for a city to be affected by both hierarchical and contagious diffusion.
12. True/False In the last 3 years, the rate of AIDS has been increasing more rapidly than ever in U.S. cities.
13. True/False Those who adopt a new idea first are known as “laggards.”
14. True/False In addition to physical features such as mountains and oceans, barriers to diffusion can political, cultural, or economic.
15. The concept of “biased innovations” emphasizes the importance of:

a. large cities

* b. social context

c. intentional discrimination

d. geography
16. In order of those who adopt an idea first, people can be categorized as:

* a. innovators, majority adopters, laggards

b. trailblazers, majority adopters, laggards

c. innovators, majority adopters, late-comers

d. trailblazers, majority adopters, late-comers
17. Which of the following phenomenon would be graphed as an S-curve?

a. total AIDS cases (Y-axis) as a function of city population (X-axis)

b. AIDS cases per 100,000 people as a function of city population

c. total AIDS cases as a function of distance from an early AIDS source region




d. AIDS cases per 100,000 people as a function of distance from an early AIDS source region

* e. cumulative AIDS cases in a region as a function of time


18. The early stages of AIDS diffusion (late 1980s) mostly followed a pattern of

a. relocation diffusion

* b. hierarchical diffusion

c. cultural diffusion

d. contagious diffusion
19. If we take the AIDS rates (cases per 100,000 persons) of all the cities in the southeastern US and graph them as a function of distance from Miami, and then drew a best-fitting curve to the points, we would find:

* a. the curve slopes downwards

b. the curve slopes upwards

c. the curve is shaped like an inverted U

d. the curve is Sshaped
20. In the above question, the cities that are well above the curve would tend to be:

* a. very large cities far from Miami

b. very small cities far from Miami

c. highly conservative and religious places

d. areas with very small gay populations and very few intravenous drug users

e. very small cities near Miami


21. AIDS originated in which continent?

a. Europe

b. Asia

* c. Africa



d. North America

e. South America


22. Which of the following is not one of the reasons why some innovations diffuse hierarchically?

a. because of the greater variety of people who live in big cities

b. because of the movement of people between large cities

c. because of the types of businesses that tend to locate in big cities

* d. because there is more facetoface interaction in big cities
23. Which of the following U.S. cities contained the earliest cases of AIDS?

a. Chicago, Cleveland and Detroit

b. Phoenix, Denver and San Diego

c. Boston, Washington D.C. and Baltimore

* d. New York, San Francisco and Miami

e. Atlanta, Memphis and New Orleans


24. Extremely high early AIDS rates in Jersey City and Newark are an example of what diffusion process at work?


a. barriers to diffusion

b. hierarchical diffusion

* c. contagious diffusion

d. relocation diffusion


25. Contagious diffusion:

* a. spreads ideas to nearby places first

b. leapfrogs over nearby places

c. occurs through migration

d. moves from large cities to small towns

e. moves from small towns to large cities


26. When ultimate Frisbee players at Columbia High School in New Jersey went off to college, and subsequently introduced Ultimate to their fellow collegians, it was an example of:

a. contagious diffusion

b. hierarchical diffusion

* c. relocation diffusion followed by expansion diffusion

d. hierarchical diffusion followed by relocation diffusion
27. Sub-Saharan Africa has the highest percentages of people infected with HIV/AIDS worldwide, but some of the lowest numbers of people receiving drugs. Additionally, 95 percent of new HIV cases occur in the less-developed world. Lastly, in sub-Saharan Africa south of the Sahara, young women make up more than three quarters of all cases. These are all examples of:

  A) Barriers to diffusion that slow or block the spread of HIV/AIDS to certain areas

  B) Hierarchical diffusion, because large cities are first affected by the disease

  C) Both relocation and expansion diffusion as the disease moves worldwide

*D) Biased innovations as not only spatial location, but also social context affect the spread of the disease

28. The development of hydrogen fueling stations in the United States is an example of a product that is in the _________ stage on the S-shaped curve of diffusion?



* A) Innovation

  B) Laggard

  C) Majority adoption

  D) None of the above

29 Which of the following best describes the order of diffusion according to the S-shaped curve, from earliest to latest adopters?



  A) Majority adopters, laggards, innovators

  B) Innovators, laggards, majority adopters

  C) Laggards, majority adopters, innovators

* D) Innovators, majority adopters, laggards

30. The typical graph of total adopters of a new innovation (Y axis) over time (X axis) follows a ____-curve shape



*  a. S

  b. J

  c. U

  d. V

  e. bell



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