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Regression equation during 2016∼2018.
| Year | Regression equation | R2 | Sig. |
| 2016 | y = −0.294+0.229X1+0.368X2+0.308X3+0.184X4+0.133X5 | 0.82 | 0.000** |
| 2017 | y = −0.307+0.142X1+0.419X2+0.355X3+0.091X4+0.120X5 | 0.73 | 0.000** |
| 2018 | y = −0.166+0.135X1+0.197X2+0.151X3+0.211X4+0.229X5 | 0.71 | 0.000** |
**Indicate significance at P < 0.01 level.
X1:PH,X2:EFBN,X3:SBW,X4:Tr,X5:Chl.
