Table 4 Energy intensity M&C by the specified parameters from 2021 to 2030 (10,000 tons of standard coal/100 million yuan, base period was 2011).

Year

Exponential model(M1)

\(y_{t} = y_{0} e^{at}\), a = ln(0.865)/4

\(y_{t} = y_{0} \lambda^{t}\),\(\lambda = 0.865^{1/4}\)

Difference model(M2)

\(y_{t} = (1{ - }\phi )^{{\text{t}}} (y_{0} - \mathop y\limits^{ \wedge } ) + \mathop y\limits^{ \wedge }\), \(\mathop y\limits^{ \wedge }\) = 0.73*\(y_{0}\),\(\phi = 1 - 0.5^{1/4}\)

Linear model(M3)

\(y_{t} = y_{0} + bt\)

b = −0.135*\(y_{0}\)/4;