The characteristics of registration rates
From 2007 to 2019, the active PTB registration rates in Henan Province showed a decreasing trend from 87.8/100,000 to 49.1/100,000 in Table 1. According to the formula of average development rate[18], the average development rate of active PTB registration rates in thirteen years was 95.3%, that is, the annual decline of registration rates was 4.7%.
Table 1. Monthly and annual active PTB registration rates from 2007 to 2019 in Henan Province, China
|
Registration Rate(per 100,000)
|
Population
|
|
JAN
|
FEB
|
MAR
|
APR
|
MAY
|
JUN
|
JUL
|
AUG
|
SEP
|
OCT
|
NOV
|
DEC
|
Annual
|
(100,000)
|
2007
|
7.6
|
5.6
|
9.0
|
9.2
|
8.4
|
8.0
|
7.4
|
7.6
|
6.8
|
6.5
|
6.8
|
5.0
|
87.8
|
939.2
|
2008
|
6.3
|
5.9
|
9.3
|
9.4
|
8.7
|
8.2
|
7.2
|
6.8
|
6.5
|
7.2
|
7.0
|
5.9
|
88.3
|
936
|
2009
|
5.0
|
6.5
|
8.6
|
8.3
|
7.5
|
7.8
|
6.7
|
6.6
|
6.5
|
6.4
|
6.0
|
6.3
|
82.3
|
942.9
|
2010
|
6.0
|
4.8
|
7.4
|
7.3
|
7.2
|
7.3
|
6.3
|
6.0
|
5.7
|
5.6
|
6.3
|
5.6
|
75.6
|
948.7
|
2011
|
5.2
|
5.0
|
7.1
|
6.7
|
6.9
|
6.5
|
5.8
|
5.8
|
5.3
|
5.4
|
6.3
|
5.9
|
71.8
|
940.5
|
2012
|
4.6
|
6.6
|
7.4
|
7.3
|
7.2
|
6.6
|
5.8
|
5.9
|
5.6
|
5.7
|
5.8
|
5.5
|
73.9
|
938.8
|
2013
|
5.1
|
4.7
|
6.8
|
6.1
|
6.5
|
5.9
|
5.5
|
5.3
|
5.5
|
5.7
|
5.6
|
5.7
|
68.4
|
940.6
|
2014
|
5.2
|
4.6
|
6.4
|
6.3
|
6.2
|
6.0
|
5.4
|
5.1
|
5.0
|
5.3
|
5.7
|
6.3
|
67.5
|
941.3
|
2015
|
5.0
|
4.1
|
6.2
|
5.9
|
5.7
|
5.8
|
5.3
|
5.2
|
5.3
|
4.9
|
5.3
|
5.7
|
64.5
|
943.6
|
2016
|
4.5
|
4.4
|
5.9
|
5.6
|
5.4
|
5.4
|
4.9
|
5.1
|
4.9
|
4.5
|
5.1
|
5.2
|
60.8
|
948
|
2017
|
3.8
|
4.9
|
5.6
|
5.2
|
5.3
|
5.4
|
4.6
|
4.9
|
4.8
|
4.4
|
5.0
|
5.0
|
58.9
|
953.2
|
2018
|
4.0
|
3.8
|
5.8
|
5.0
|
5.4
|
5.1
|
4.5
|
4.6
|
4.5
|
4.3
|
4.6
|
4.5
|
56.1
|
955.9
|
2019
|
4.2
|
3.6
|
5.1
|
4.8
|
4.5
|
4.4
|
4.4
|
3.8
|
3.8
|
3.2
|
3.6
|
3.7
|
49.1
|
960.5
|
Time series analysis
The monthly active PTB registration rates from 2007 to 2019 in Henan Province showed a trend of volatility and decline (Figure 1). By differences and transformation including one order difference, one order seasonal difference and the natural log (LN) transformation, the time series showed the stationary (figure 2). It conformed to the requirement of the time series analysis.
After differences and transformation, according to autocorrelation function (ACF), partial autocorrelation function (PACF) and cross correlation function (CCF) analysis (figure 3-5), there were neither correlation between the registration rates nor between registration rates and time. The series was white noise.
Through seasonal decomposition, we got the seasonal factors in each month (table 2). March, April, May and June accounted for high active PTB registration rates.
Table 2. Seasonal factors (%) for the active PTB registration rates from 2007 to 2019 in Henan Province, China
Month
|
JAN
|
FEB
|
MAR
|
APR
|
MAY
|
JUN
|
Seasonal factors
|
85.8
|
84.0
|
117.5
|
111.8
|
111.5
|
109.1
|
Month
|
JUL
|
AUG
|
SEP
|
OCT
|
NOV
|
DEC
|
Seasonal factors
|
97.6
|
97.2
|
94.5
|
93.1
|
99.9
|
98.1
|
Selection of the model
Through the Expert Modeler, the ES winters multiplication model was selected as the best-fitting model. By one order difference, one order seasonal difference and LN transformation, the model fit statistics and parameters were shown in table 3 to 5.
Table 3. Exponential smoothing model fitting for the active PTB registration rates from 2007 to 2016 in Henan Province, China
Model
|
Stationary R-squared
|
R-squared
|
RMSE
|
MAPE
|
MAE
|
MaxAPE
|
MaxAE
|
Normalized BIC
|
Registration Rate
|
0.616
|
0.837
|
0.455
|
5.422
|
0.328
|
28.604
|
1.853
|
-1.457
|
RMSE: Root mean square error; MAPE: Mean absolute percentage error; MAE: Mean absolute error;MaxAPE: Max absolute percentage error;MaxAE: Max absolute error; Normalized BIC: Normalized Bayesian Information Criterion
Table 4. Exponential Smoothing Model Statistics
Model
|
Ljung-Box Q(18)
|
Statistics
|
DF
|
Sig.
|
Registration Rate
|
12.908
|
15
|
.609
|
Table 5. Exponential Smoothing Model Parameters
Model
|
Estimate
|
SE
|
t
|
Sig.
|
Registration Rate Model1
|
No Transformation
|
Alpha (Level)
|
0.057
|
0.034
|
1.704
|
0.091
|
Gamma (Trend)
|
0.001
|
0.039
|
0.025
|
0.980
|
Delta (Season)
|
0.308
|
0.065
|
4.731
|
0.000
|
Because the dependent variable data were seasonal data, the Stationary R-squared was more representative. The Stationary R-squared of the model was 0.616, the R-squared was 0.837, and the normalized Bayesian Information Criterion (BIC) was -1.457, which showed that the fitting of the model was good. The MAPE of the model was 5.422%, which indicated that the forecast effect was good. The residual sequence was tested by white noise (Ljung-Box (18) = 12.908, P=0.609). Therefore, the hypothesis based on the independent residual sequence was acceptable. The model had already fully extracted information. It was suitable for the ES model to be used for the prediction.
Of the three parameters of the fitting model, the seasonal parameter (Delta) had statistical significance (P value = 0.000), and the stationary parameter (Alpha) and the trend parameter (Gamma) of time series had no statistical significance (P value=0.091 and P value=0.980, respectively), indicating that there was no horizontal and linear trend in this time series.
Validity of the model
According to the established ES model, the predicted values of monthly active PTB registration rates in Henan Province were replace by the observed ones from 2017to 2019. The mean absolute error (MAE) was 0.328%. The predicted values were basically consistent with the observed ones (Figure 6).
Prediction for 2020 and 2025
The ES model was applied to predict monthly and annual active PTB registration rates from 2020 to 2025 in Henan Province. The predicted values of the annual registration rates can be seen in table 6. The annual active PTB registration rates were 49.2 (95% CI: 36.0-62.5) and 34.3 (95% CI: 17.7-50.8) per 100,000 population in 2020 and 2025, respectively. The fitting and forecast results were shown in figure 7. Compared with the active PTB registration rate in 2015, the reduction will be 23.7% (95% CI: 3.1%-44.2%) and 46.9% (95% CI: 21.3%-72.5%) in 2020 and 2025, respectively.
Table 6. The predicted annual active PTB registration rates from 2020 to 2025 in Henan Province, China (1/100,000)
|
2020
|
2021
|
2022
|
2023
|
2024
|
2025
|
Predicted
|
49.2
|
46.2
|
43.2
|
40.3
|
37.3
|
34.3
|
95% UCL
|
62.5
|
60.2
|
57.9
|
55.5
|
53.2
|
50.8
|
95% LCL
|
36.0
|
32.3
|
28.6
|
25.0
|
21.4
|
17.7
|
95% UCL:95% upper confidence limit; 95% LCL: 95% lower confidence limit