Table 2.
t0 is the initial year considered here for the different subways networks, 
is the average velocity (number of stations built per year), 
is the standard deviation of v and f is the fraction of years of inactivity (no stations built).
| city | t0 |  |
 |
f (%) |
|---|---|---|---|---|
| Beijing | 1971 | 3.3 | 7.74 | 79 |
| Tokyo | 1927 | 2.8 | 5.47 | 51 |
| Seoul | 1974 | 11.2 | 14.9 | 20 |
| Paris | 1900 | 2.6 | 5.1 | 60 |
| Mexico City | 1969 | 3.7 | 5.9 | 55 |
| NYC | 1878 | 3.3 | 8.3 | 68 |
| Chicago | 1901 | 1.9 | 6.24 | 71 |
| London | 1863 | 2.3 | 3.8 | 48 |
| Shanghai | 1995 | 14.9 | 20.2 | 31 |
| Moscow | 1936 | 1.7 | 1.9 | 43 |
| Berlin | 1901 | 1.6 | 3.3 | 65 |
| Madrid | 1919 | 2.3 | 4.6 | 59 |
| Osaka | 1934 | 1.4 | 4.1 | 79 |
| Barcelona | 1914 | 1.4 | 4.8 | 78 |