International Scholarly Research Notices

Research Article

A Combined Model of Global Cultivated Area Change and Prediction for Future: 1961–2020

Table 3

Cubic curve model, the Gompertz model, and cyclic model estimation results.
VariableCubic curveLinear Gompertz modelLinear cyclic curve model
Coefficient valueCoefficient valueCoefficient value
Constant term 39.450.49***53.511.36***55.89
Single term−13719504***−2.86−0.006***−17.04−0.005**−2.11
Quadratic term997828.2***4.41  −0.0001***−2.48
Cubic term−12016.22***−3.95    
 Ad- = 0.90Ad- = 0.86Ad- = 0.88
  = 148.98*** = 290.42*** = 172.46***
 D-W = 0.32D-W = 0.21D-W = 0.24
Note: ***means significance under the level of 0.01, **means significance under the level of 0.05, and *means significance under the level of 0.1.