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v3.19.3.a.u2

Summary of Significant Accounting Policies (Tables) | 12 Months Ended
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Dec. 31, 2019
Accounting Policies [Abstract] |
Schedule of inventory | Our inventory as of December 31 consisted of:
(in millions) |  | 2019 |  | 2018
Materials and supplies |  | $ | 234.2 |  |  | $ | 226.6 |
Natural gas in storage |  | 227.7 |  |  | 232.9 |
Fossil fuel |  | 87.9 |  |  | 88.7 |
Total |  | $ | 549.8 |  |  | $ | 548.2 |
Schedule of annual utility composite depreciation rates | Annual utility composite depreciation rates are shown below:
Annual Utility Composite Depreciation Rates |  | 2019 |  | 2018 |  | 2017
WE |  | 3.11% |  | 3.18% |  | 2.95%
WPS |  | 2.44% |  | 2.50% |  | 2.55%
WG |  | 2.29% |  | 2.30% |  | 2.30%
PGL |  | 3.20% |  | 3.25% |  | 3.29%
NSG |  | 2.48% |  | 2.45% |  | 2.43%
MERC * |  | 2.33% |  | 1.95% |  | 2.51%
MGU |  | 2.54% |  | 2.61% |  | 2.61%
UMERC |  | 2.87% |  | 2.50% |  | 2.46%
* The 2018 rate reflects the impact of a new depreciation study approved by the MPUC in May 2018. The rates approved were effective retroactive to January 2017. An approximate $1.4 million reduction in depreciation expense was recorded in 2018 related to this depreciation study.
Schedule of public utilities allowance for funds used during construction | Average AFUDC rates are shown below:
|  | 2019
|  | Average AFUDC Retail Rate |  | Average AFUDC Wholesale Rate
WE |  | 8.45% |  | 5.11%
WPS |  | 7.72% |  | 2.58%
WG |  | 8.33% |  | N/A
UMERC |  | 6.28% |  | N/A
WBS |  | 7.72% |  | N/A
Our regulated utilities and WBS recorded the following AFUDC for the years ended December 31:
(in millions) |  | 2019 |  | 2018 |  | 2017
AFUDC – Debt |  |  |  |  |  |  |  |  |
WE |  | $ | 1.5 |  |  | $ | 1.5 |  |  | $ | 1.2 |
WPS |  | 2.4 |  |  | 1.9 |  |  | 1.6 |
WG |  | 0.5 |  |  | 0.2 |  |  | 0.3 |
UMERC |  | 1.3 |  |  | 2.4 |  |  | 0.1 |
WBS |  | 0.1 |  |  | 0.2 |  |  | 1.1 |
Other |  | 0.1 |  |  | 0.7 |  |  | 0.6 |
Total AFUDC – Debt |  | $ | 5.9 |  |  | $ | 6.9 |  |  | $ | 4.9 |
AFUDC – Equity |  |  |  |  |  |  |  |  |
WE |  | $ | 3.7 |  |  | $ | 3.9 |  |  | $ | 3.1 |
WPS |  | 5.7 |  |  | 4.6 |  |  | 4.1 |
WG |  | 1.3 |  |  | 0.6 |  |  | 0.9 |
UMERC |  | 3.3 |  |  | 5.4 |  |  | 0.2 |
WBS |  | 0.2 |  |  | 0.6 |  |  | 3.0 |
Other |  | 0.2 |  |  | 0.1 |  |  | 0.1 |
Total AFUDC – Equity |  | $ | 14.4 |  |  | $ | 15.2 |  |  | $ | 11.4 |
Schedule of assumptions used to estimate the fair value of stock options granted | The following table shows the estimated weighted-average fair value per stock option granted along with the weighted-average assumptions used in the valuation models:
|  | 2019 |  | 2018 |  | 2017
Stock options granted |  | 476,418 |  |  | 710,710 |  |  | 552,215 |
Estimated weighted-average fair value per stock option |  | $ | 8.60 |  |  | $ | 7.71 |  |  | $ | 7.45 |
Assumptions used to value the options: |  |  |  |  |  |
Risk-free interest rate |  | 2.5% – 2.7% |  |  | 1.6% – 2.8% |  |  | 0.7% – 2.5% |
Dividend yield |  | 3.6 | % |  | 3.5 | % |  | 3.5 | %
Expected volatility |  | 17.0 | % |  | 18.0 | % |  | 19.0 | %
Expected life (years) |  | 8.5 |  |  | 5.9 |  |  | 6.8 |

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