ARMA analysis of the green innovation technology of core enterprises under the ecosystem – Time series data

Fig. 1

Fig. 2

Autocorrelation and Partial Autocorrelation Test of Granted Green Patent

LAG	AC	PAC	Q	Prob>Q	[Autocorrelation]	[PartialAutocor]
1	0.7687	0.9657	12.512	0.0004	| – – –	| – – –
2	0.4996	0.0542	18.129	0.0001	| – -	|
3	0.3083	0.0737	20.41	0.0001	| –	|
4	0.1342	−0.0321	20.873	0.0003	|-	|
5	−0.0023	0.2998	20.873	0.0009	|	| –

Several landmark events in BYD's green innovation process

Year	Landmark events
2003	Chuanfu Wang announced that he would enter the automobile and new energy automobile industries.
2005	When the outside world was not optimistic about the prospects of electric vehicles, BYD set up a research and development team and began to deploy in the IGBT field.
2008	BYD launched the world's first dual-mode electric vehicle F3 DM that does not rely on professional charging stations, unveiling the large-scale commercialisation of new energy vehicles;BYD acquired the semiconductor manufacturing company Ningbo Zhongwei for nearly 200 million yuan, integrated the upstream industry chain of electric vehicles, and accelerated the commercialisation of BYD electric vehicles.
2009	BYD plans to launch pure electric vehicles.
2010	BYD found the solution of ‘Urban Bus Electrification.’
2012	BYD introduced the pure electric model BYD E6, the plug-in hybrid model BYD Qin, BYD Tang and other models to the market.
2013	BYD completed the research and development of core energy storage technology, which proved the safety and feasibility of battery energy storage technology and brought about the commercial application of battery energy storage.
2018	BYD's IGBT 4.0, an automotive-grade product, was released in Ningbo. At the China Electric Vehicles Forum, Chuanfu Wang called on the state to provide more policy support for plug-in hybrid vehicles, including financial subsidies and abolition of consumption tax.
2021	Chuanfu Wang pointed out that digital transformation is an important direction for the transformation of the automotive industry, and he would build more digital factories for electric vehicles and core components, and advance the strategic goal of Industry 4.0.BYD initiated a study on carbon neutrality planning.

The regression result of AR(1)

	Zls	Coef.	Std. Err.	z	P>|z|	[95% Conf. Interval]
zls
	_cons	105.8925	77.4997	1.37	0.172	−46.004	257.7891
	Ar
	L1.	0.952	0.136	7.00	0.000	0.6854	1.2185
	sigma	27.5112	5.0574	5.44	0.000	17.5982	37.4236

Residual autocorrelation and partial autocorrelation test of green patent grants

LAG	AC	PAC	Q	Prob>Q	[Autocorrelation]	[Partial Autocor]
1	−0.0075	−0.0114	0.0012	0.9724	|	|
2	−0.035	−0.0177	0.0287	0.9858	|	|
3	0.1021	0.1452	0.27899	0.9639	|	|-
4	−0.0982	−0.058	0.52696	0.9708	|	|
5	−0.1649	−0.1973	1.2801	0.937	-|	-|

The regression result of ARMA(1,1)

	zls	Coef.	Std. Err.	z	P>|z|	[95% Conf. Interval]
zls
	_cons	103.7264	67.6132	1.53	0.125	−28.7931	236.2459
ARMA
	ar
	L1.	0.9259	0.184	5.03	0.000	0.5652	1.2865
	ma
	L1.	0.1804	0.2873	0.63	0.53	−0.3827	0.7435
	sigma	27.166	4.9591	5.48	0.000	17.4462	36.8857