Filed pursuant to Rule 424(b)(3)
Registration Statement Nos. 333-255533
| Year ended December 31, | 2021 | 2020 | 2019 |
| Per share data | |||
| Net asset value, beginning of period | $33.26 | $31.03 | $26.58 |
| Income from investment operations: | |||
| Net investment income | 1.07 | 1.05 | 1.03 |
| Net realized and unrealized gain (loss) | 7.28 | 2.86 | 5.39 |
| Total from investment operations | 8.35 | 3.91 | 6.42 |
| Less distributions to Stockholders from: | |||
| Net investment income — Preferred Stock | (0.04) | (0.04) | (0.04) |
| Net investment income — Common Stock | (1.05) | (1.07) | (1.01) |
| Net realized gains — Common Stock | (3.64) | (0.57) | (0.92) |
| Total distributions to Stockholders | (4.73) | (1.68) | (1.97) |
| Dilution in net asset value from dividend reinvestment | (0.32) | — | — |
| Increase resulting from share repurchases | 0.13 | — | — |
| Net asset value, end of period | $36.69 | $33.26 | $31.03 |
| Adjusted net asset value, end of period(a) | $36.57 | $33.14 | $30.92 |
| Market price, end of period | $33.19 | $29.47 | $28.20 |
| Total return | |||
| Based upon net asset value | 26.76% | 14.17% | 25.20% |
| Based upon market price | 29.41% | 11.31% | 28.59% |
| Ratios to average net assets | |||
| Expenses to average net assets for Common Stock(b) | 0.46% (c) | 0.48% | 0.49% |
| Net investment income to average net assets for Common Stock | 2.77% | 3.45% | 3.32% |
| Supplemental data | |||
| Net assets, end of period (000's): | |||
| Common Stock | $2,005,857 | $1,745,135 | $1,664,401 |
| Preferred Stock | $37,637 | $37,637 | $37,637 |
| Total net assets | $2,043,494 | $1,782,772 | $1,702,038 |
| Portfolio turnover | 56% | 67% | 60% |
| (a) | Assumes the exercise of outstanding warrants. |
| (b) | In addition to the fees and expenses that the Fund bears directly, the Fund indirectly bears a pro rata share of the fees and expenses of any other funds in which it invests. Such indirect expenses are not included in the Fund’s reported expense ratios. |
| (c) | Ratios include interest on collateral expense which is less than 0.01%. |
| 2018 | 2017 | 2016 | 2015 | 2014 | 2013 | 2012 |
| $29.88 | $25.91 | $23.49 | $24.76 | $23.11 | $18.77 | $16.77 |
| 0.99 | 0.93 | 0.90 | 0.81 | 0.73 | 0.69 | 0.63 |
| (2.35) | 4.24 | 2.33 | (1.37) | 1.70 | 4.36 | 2.00 |
| (1.36) | 5.17 | 3.23 | (0.56) | 2.43 | 5.05 | 2.63 |
| (0.03) | (0.03) | (0.03) | (0.03) | (0.03) | (0.03) | (0.03) |
| (0.96) | (1.07) | (0.91) | (0.81) | (0.75) | (0.68) | (0.60) |
| (0.95) | (0.10) | — | — | — | — | — |
| (1.94) | (1.20) | (0.94) | (0.84) | (0.78) | (0.71) | (0.63) |
| — | — | (0.06) | (0.05) | — | — | — |
| — | — | 0.19 | 0.18 | — | — | — |
| $26.58 | $29.88 | $25.91 | $23.49 | $24.76 | $23.11 | $18.77 |
| $26.48 | $29.77 | $25.83 | $23.42 | $24.68 | $23.04 | $18.71 |
| $23.52 | $26.94 | $22.05 | $20.02 | $21.41 | $19.98 | $16.00 |
| (4.10)% | 20.82% | 15.25% | (1.36%) | 11.09% | 27.76% | 16.24% |
| (5.88)% | 28.00% | 15.08% | (2.78%) | 11.11% | 29.58% | 16.77% |
| 0.49% | 0.49% | 0.50% | 0.50% | 0.49% | 0.50% | 0.52% |
| 3.14% | 3.21% | 3.59% | 3.16% | 2.91% | 3.12% | 3.28% |
| $1,431,211 | $1,637,553 | $1,470,843 | $1,382,712 | $1,511,285 | $1,435,734 | $1,183,285 |
| $37,637 | $37,637 | $37,637 | $37,637 | $37,637 | $37,637 | $37,637 |
| $1,468,848 | $1,675,190 | $1,508,480 | $1,420,349 | $1,548,922 | $1,473,371 | $1,220,922 |
| 63% | 95% | 82% | 76% | 76% | 62% | 68% |