Table 7.
Parameter coefficients and fit for the four exponential random graph models (ERGMs) of pig trade in an intensive production system (France—Côtes-d’Armor).
| Covariates | ERGM coefficients (SE)a |
|||
|---|---|---|---|---|
| Bernoulli (edges) | Edges + attributes | Edges + network statistics | Edges + attributes + network statistics | |
| Edges | −7.52 (0.02)*** | −11.08 (0.28)*** | −4.27 (0.15)*** | −6.44 (0.46)*** |
| Homophily | ||||
| Housing system | 1.11 (0.24)*** | 0.72 (0.30)* | ||
| Nodal attribute mixing | ||||
| Pig companyb | ||||
| No. 1 to no. 1 | 1.56 (0.15)*** | 1.07 (0.21)*** | ||
| No. 1 to no. 2 | −2.23 (0.72)** | −2.69 (0.88)** | ||
| No. 2 to no. 2 | 2.93 (0.21)*** | 2.78 (0.30)*** | ||
| NC to NC | Reference | Reference | ||
| Type of farmc | ||||
| MU to MU | 3.72 (0.27)*** | 1.53 (0.77)*** | ||
| FA to MU | 0.98 (1.01) | −1.06 (2.93) | ||
| FF to MU | −1.10 (0.71) | −2.69 (1.65) | ||
| FI to MU | −0.57 (0.59) | −0.21 (1.24) | ||
| SP to MU | NA | NA | ||
| TR to MU | NA | NA | ||
| MU to FA | 4.21 (0.22)*** | 2.81 (0.37)*** | ||
| FA to FA | 0.92 (1.00) | −0.12 (1.25) | ||
| FF to FA | −0.14 (0.42) | −1.09 (0.74) | ||
| FI to FA | −1.12 (0.71) | −2.03 (1.61) | ||
| SP to FA | NA | NA | ||
| TR to FA | NA | NA | ||
| MU to FF | 4.64 (0.11)*** | 3.08 (1.69)*** | ||
| FA to FF | 2.07 (0.17)*** | 0.79 (0.26)** | ||
| FF to FF | 0.90 (0.12)*** | −0.11 (0.17) | ||
| FI to FF | −1.28 (0.22)*** | −1.50 (0.35)*** | ||
| SP to FF | NA | NA | ||
| TR to FF | 2.58 (0.76)*** | 5.45 (0.27)*** | ||
| MU to FI | 2.17 (0.17)*** | 0.53 (0.23)* | ||
| FA to FI | 3.40 (0.12)*** | 2.07 (0.17)*** | ||
| FF to FI | 2.57 (0.10)*** | 1.66 (0.13)*** | ||
| FI to FI | Reference | Reference | ||
| SP to FI | NA | NA | ||
| TR to FI | 3.12 (0.51)*** | 7.99 (0.26)*** | ||
| MU to SP | 3.30 (1.01)** | 1.72 (1.41) | ||
| FA to SP | NA | NA | ||
| FF to SP | NA | NA | ||
| FI to SP | 0.29 (1.00) | 0.41 (1.42) | ||
| SP to SP | 5.28 (1.02)*** | 4.25 (2.12)* | ||
| TR to SP | NA | NA | ||
| MU to TR | 7.13 (0.30)*** | 4.65 (0.33)*** | ||
| FA to TR | 6.69 (0.32)*** | 5.54 (0.28)*** | ||
| FF to TR | 7.05 (0.12)*** | 5.91 (0.10)*** | ||
| FI to TR | 3.81 (0.31)*** | 3.41 (0.39)*** | ||
| SP to TR | NA | NA | ||
| TR to TR | NA | NA | ||
| Structural terms | ||||
| Isolates | 0.94 (0.08)*** | 0.28 (0.10)** | ||
| Asymmetric edges | −1.53 (0.15)*** | −2.42 (0.29)*** | ||
| GWOD | −2.76 (0.07)*** | −1.77 (0.13)*** | ||
| GWDSP | −0.27 (0.01)*** | −0.18 (0.04)*** | ||
| GWESP | 2.51 (0.10)*** | 0.85 (0.17)*** | ||
| Fit | ||||
| Akaike information criteria | 53,087 | 40,233 | 48,891 | 39,649 |
a*** <0.001; ** <0.01; * <0.05.
bFor readability, not all values for selective for the pig companies are shown; NC, no company.
cMU, multipliers; FA, farrow farms; FF, farrow-to-finish farms; FI, finishers; SP, small producers; TR, trade operators.