Table 2 Some national referral network measures in 2006-2011

# nodes

272353

296008

313051

323042

334452

347586

# edges

5708791

5948185

6313136

6544847

6785594

7047586

Exponent of indegree power law

3.08

2.80

1.55

2.76

1.54

2.74

p-value of indegree power law test

0.97

0.89

0.21

0.85

0.22

0.82

Exponent of outdegree power law

3.01

2.69

2.71

2.66

2.56

2.68

p-value of outdegree power law test

0.9

0.94

0.93

0.96

0.91

0.93

Size of the largest connected component

271898

295405

312412

322452

333727

346711

(in, in) degree assortativity

-0.094

-0.088

-0.084

-0.085

-0.083

-0.084

Self in/out degree correlation

0.983

0.982

0.983

0.983

0.983

0.984

Reciprocity of #referral

0.878

0.890

0.896

0.901

0.902

0.896