VALUE OF BUSINESS ACQUIRED The balances of and changes in VOBA as of and for the years ended December 31, are as follows: | | | | | | | | | | | | | | 2017 | | 2016 | | 2015 | | (in millions) | Balance, beginning of year | $ | 2,314 |
| | $ | 2,828 |
| | $ | 2,836 |
| Amortization—Impact of assumption and experience unlocking and true-ups | (56 | ) | | (246 | ) | | 128 |
| Amortization—All other | (311 | ) | | (351 | ) | | (385 | ) | Change in unrealized investment gains and losses | (456 | ) | | (112 | ) | | 214 |
| Interest | 75 |
| | 81 |
| | 86 |
| Foreign currency translation | 25 |
| | 114 |
| | (57 | ) | Other | 0 |
| | 0 |
| | 6 |
| Balance, end of year | $ | 1,591 |
| | $ | 2,314 |
| | $ | 2,828 |
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The following table provides VOBA balances and the weighted average remaining expected life for the year ended December 31, 2017.
| | | | | | | | VOBA Balance | | Weighted Average Remaining Expected Life In Years | | ($ in millions) | | | CIGNA | $ | 223 |
| | 12 | Prudential Annuities Holding Co. | $ | 38 |
| | 5 | Gibraltar Life | $ | 1,178 |
| | 9 | Aoba Life | $ | 0 |
| | 7 | The Hartford Life Business | $ | 145 |
| | 9 | Gibraltar BSN Life Berhad | $ | 7 |
| | 8 |
The following table provides the interest accrual rates varying by acquisition for the years ended December 31.
| | | | | | | | | | | | | | 2017 | | 2016 | | 2015 | CIGNA | | | 6.40% | | | | 6.40% | | | | 6.40% | Prudential Annuities Holding Co. | | | 5.96% | | | | 6.00% | | | | 6.05% | Gibraltar Life | 1.28% | to | 2.87% | | 1.28% | to | 2.87% | | 1.28% | to | 2.87% | Aoba Life | | | 2.60% | | | | 2.60% | | | | 2.60% | The Hartford Life Business | 3.00% | to | 6.17% | | 3.00% | to | 6.17% | | 3.00% | to | 6.17% | Gibraltar BSN Life Berhad | 4.07% | to | 5.51% | | 4.07% | to | 5.51% | | 4.07% | to | 5.51% |
The following table provides estimated future amortization, net of interest, for the periods indicated. | | | | | | | | | | | | | | | | | | | | | | 2018 | | 2019 | | 2020 | | 2021 | | 2022 | | (in millions) | Estimated future VOBA amortization | $ | 204 |
| | $ | 182 |
| | $ | 164 |
| | $ | 152 |
| | $ | 138 |
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