Table 1.
Summary statistics and geographic distribution of alters for each ego’s network.
| Network characteristics | Geographic characteristics | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Agent | Nodes | Edges | Average degree | Diameter | Density | Clustering coefficient | Modules; modularity | Average distance to friends (post-period) | Standard distance pre-period | Standard distance post-period | Change in standard distance | Change of mean center |
| A | 376 | 2679 | 12.3 | 10 | 0.038 | 0.36 | 4; 0.61 | 431 | 1468 | 2392 | 924 | 192 |
| B | 336 | 2533 | 14.5 | 9 | 0.045 | 0.53 | 13; 0.67 | 7827 | 5570 | 5691 | 121 | 667 |
| C | 601 | 7392 | 23.5 | 11 | 0.041 | 0.49 | 15; 0.62 | 277 | 1592 | 2395 | 803 | 383 |
| D | 370 | 3686 | 19.4 | 9 | 0.054 | 0.57 | 11; 0.71 | 2567 | 4377 | 3686 | -691 | 597 |
| E | 573 | 9833 | 33.8 | 10 | 0.06 | 0.47 | 12; 0.51 | 1409 | 2754 | 3727 | 973 | 1873 |
| F | 232 | 2706 | 22.3 | 5 | 0.10 | 0.53 | 12; 0.37 | 1174 | 2917 | 3903 | 986 | 455 |
| G | 361 | 2989 | 14.8 | 12 | 0.04 | 0.54 | 12; 0.71 | 215 | 887 | 2283 | 1396 | 368 |
| H | 437 | 6002 | 27.2 | 8 | 0.06 | 0.46 | 10; 0.51 | 1185 | 627 | 1267 | 640 | 188 |
| I | 403 | 5022 | 24.7 | 8 | 0.062 | 0.43 | 9; 0.52 | 687 | 3087 | 2383 | –704 | 518 |
| J | 437 | 2763 | 11.5 | 10 | 0.029 | 0.52 | 13; 0.78 | 1619 | 3726 | 4157 | 431 | 409 |
| K | 639 | 9784 | 30.5 | 7 | 0.048 | 0.33 | 10; 0.46 | 712 | 2534 | 2893 | 359 | 575 |
| L | 188 | 1002 | 10.4 | 10 | 0.057 | 0.64 | 6; 0.74 | 697 | 3047 | 2605 | –442 | 129 |
| M | 201 | 784 | 6.9 | 10 | 0.039 | 0.16 | 16; 0.46 | 8522 | 5727 | 5610 | –117 | 325 |
| N | 772 | 7143 | 18.2 | 11 | 0.024 | 0.44 | 16; 0.76 | 529 | 3274 | 3357 | 83 | 292 |
| O | 123 | 1028 | 15.8 | 9 | 0.137 | 0.74 | 9; 0.40 | 6701 | 3588 | 5564 | 1976 | 448 |
| P | 659 | 11,708 | 34.9 | 8 | 0.054 | 0.50 | 14; 0.52 | 1508 | 3726 | 3552 | –174 | 1150 |
| Q | 727 | 12,667 | 34.5 | 9 | 0.048 | 0.53 | 10; 0.69 | 492 | 1792 | 2951 | 1159 | 520 |
| R | 227 | 4412 | 37.7 | 6 | 0.172 | 0.55 | 10; 0.23 | 176 | 49 | 1658 | 1609 | 196 |
| S | 408 | 7639 | 37.0 | 7 | 0.092 | 0.52 | 9; 0.52 | 626 | 1693 | 2929 | 1236 | 441 |
| T | 566 | 4157 | 14.3 | 14 | 0.026 | 0.53 | 15; 0.75 | 1148 | 1156 | 2167 | 1011 | 560 |
Figure 1.
Example force-directed social network visualizations. The large network represents all egos. The top right network represents the ego with the sparsest network, and at bottom right, the ego with the densest network. Visualizations created in the Gephi environment.
Figure 2.
A collective distance decay distribution shows that in the pre-period (blue line), more alters lived nearby, and in the post-period (red line), more alters live between 1,500–3,000 km from the ego.
Figure 3.
An example map of one ego’s friends’ locations at inception (pre-cities) and at the time of the study (post-cities) shows the spreading of friend locations.
Table 2.
Top 20 most popular domestic alter cities and the number of egos with alters in these locations in the pre-period and post-period.
| Pre-city | Alters | Egos | Post-city | Alters | Egos |
|---|---|---|---|---|---|
| State College, PA | 1384 | 17 | State College, PA | 797 | 18 |
| Washington–Arlington–Alexandria, DC–VA–MD–WV | 803 | 12 | Washington–Arlington–Alexandria, DC–VA–MD–WV | 721 | 18 |
| Seattle–Tacoma–Bellevue, WA | 310 | 9 | New York–Northern New Jersey–Long Island, NY–NJ–PA | 346 | 17 |
| Poughkeepsie–Newburgh–Middletown, NY | 306 | 3 | Boston–Cambridge–Quincy, MA–NH | 276 | 17 |
| Chicago–Naperville–Joliet, IL–IN–WI | 288 | 10 | Charlotte–Gastonia–Concord, NC–SC | 239 | 8 |
| Boston–Cambridge–Quincy, MA–NH | 245 | 13 | Seattle–Tacoma–Bellevue, WA | 231 | 17 |
| Knoxville, TN | 222 | 5 | Chicago–Naperville–Joliet, IL–IN–WI | 224 | 16 |
| Cedar Rapids, IA | 205 | 2 | Philadelphia–Camden–Wilmington, PA–NJ–DE–MD | 207 | 15 |
| Charlotte–Gastonia–Concord, NC–SC | 199 | 4 | Atlanta–Sandy Springs–Marietta, GA | 193 | 12 |
| Atlanta–Sandy Springs–Marietta, GA | 196 | 7 | San Francisco–Oakland–Fremont, CA | 183 | 14 |
| San Francisco–Oakland–Fremont, CA | 186 | 8 | Los Angeles–Long Beach–Santa Ana, CA | 133 | 17 |
| Williamsport, PA | 180 | 3 | Dallas–Fort Worth–Arlington, TX | 132 | 15 |
| Austin–Round Rock, TX | 178 | 5 | Albany–Schenectady–Troy, NY | 129 | 6 |
| Philadelphia–Camden–Wilmington, PA–NJ–DE–MD | 173 | 9 | Knoxville, TN | 126 | 5 |
| Dallas–Fort Worth–Arlington, TX | 159 | 6 | Austin–Round Rock, TX | 120 | 15 |
| Appleton, WI | 125 | 2 | Williamsport, PA | 107 | 4 |
| Riverside–San Bernardino–Ontario, CA | 104 | 5 | Cedar Rapids, IA | 92 | 2 |
| New York–Northern New Jersey–Long Island, NY–NJ–PA | 63 | 16 | Pittsburgh, PA | 91 | 15 |
| Harrisburg–Carlisle, PA | 61 | 3 | Augusta–Richmond County, GA–SC | 82 | 5 |
| San Diego–Carlsbad–San Marcos, CA | 45 | 7 | Riverside–San Bernardino–Ontario, CA | 76 | 7 |
Figure 4.
Individuals have fewer alters in red regions and more alters in blue regions over time, illustrating a shift toward coastal locales, North Carolina, and large cities in the West. Hot and cold spots are created using a kernel density function.
Figure A1.
Top cities for ego interaction at the time of friendship inception (as contours and white hot spots) are compared with the top cities for gravity model interaction (as hot and cold colors). Each number represents the rank of the city by its likelihood for interaction, given the gravity model’s prediction. White outlines represent popular cities for friends and yellow outlines represent cities with high theoretical interaction but few friends. Unpopular cities for friendships (marked in yellow) are peripheral to the location of the university.
Figure A2.
Top cities for ego interaction at the time of the study vis-à-vis top cities for gravity model interaction. Unpopular cities for friendships are still peripheral to the location of the university.
Table 3.
Table of group types and changes in standard distances.
| Group type | Modules | Avg. standard distance before; after (km) | Difference in standard distance (km) | Avg. years since inception |
|---|---|---|---|---|
| University | 36 | 2298; 3810 | 1512 | 8.5 |
| Professional | 21 | 2468; 3927 | 1460 | 6.6 |
| Secondary education | 20 | 527; 2441 | 1914 | 14.2 |
| Place-based cultural group | 16 | 1437; 2224 | 788 | 10.7 |
| Family | 15 | 1678; 2459 | 781 | 22.2 |
| Non-residential gathering | 14 | 2898; 4865 | 1967 | 6.5 |
| Non-place-based cultural group | 8 | 2463; 4267 | 1805 | 9.5 |
| Other | 3 | 4429; 5410 | 981 | 5.5 |