| Schedule of financial highlights |
| | Year Ended December 31, | | | | 2023 | | | 2022 | | | 2021 | | | 2020 | | | 2019 | | Per Share Data (1) | | | | | | | | | | | | | | | | Net asset value at beginning of period | | $ | 2.89 | | | | 2.80 | | | | 2.44 | | | | 2.05 | | | | 2.30 | | Net investment gain (loss) | | | (0.07 | ) | | | 0.13 | | | | 0.27 | | | | 0.11 | | | | (0.14 | ) | Net realized and unrealized gain (loss) | | | (0.19 | ) | | | (0.11 | ) | | | 0.54 | | | | 0.41 | | | | 0.00 | | (Provision for) benefit from income taxes | | | 0.07 | | | | 0.00 | | | | (0.23 | ) | | | (0.05 | ) | | | 0.00 | | Issuance of common stock | | | 0.07 | | | | 0.00 | | | | 0.00 | | | | 0.00 | | | | 0.00 | | Stock-based compensation | | | 0.23 | | | | 0.05 | | | | 0.00 | | | | (0.02 | ) | | | 0.00 | | Repurchase of common stock | | | 0.00 | | | | 0.00 | | | | 0.00 | | | | 0.05 | | | | 0.00 | | Other changes in equity | | | (0.09 | ) | | | 0.02 | | | | 0.00 | | | | 0.00 | | | | 0.00 | | Payment of common stock dividend | | | 0.00 | | | | 0.00 | | | | (0.22 | ) | | | (0.11 | ) | | | (0.11 | ) | Net asset value at end of period | | $ | 2.91 | | | | 2.89 | | | | 2.80 | | | | 2.44 | | | | 2.05 | | | | | | | | | | | | | | | | | | | | | | | Ratio / Supplemental Data | | | | | | | | | | | | | | | | | | | | | Per share market value of investments at end of period | | $ | 2.75 | | | | 2.70 | | | | 2.95 | | | | 1.40 | | | | 0.36 | | Shares outstanding at end of period | | | 6,385,255 | | | | 6,185,255 | | | | 4,795,739 | | | | 4,793,739 | | | | 4,918,845 | | Average weighted shares outstanding for the period | | | 6,366,481 | | | | 5,333,028 | | | | 4,795,242 | | | | 4,830,691 | | | | 4,918,845 | | Net assets at end of period | | $ | 18,590,263 | | | | 17,871,560 | | | | 13,414,049 | | | | 11,640,887 | | | | 10,068,533 | | Average net assets (2) | | $ | 18,647,600 | | | | 15,639,394 | | | | 13,155,207 | | | | 10,504,563 | | | | 11,473,535 | | Total investment return | | | (7.27 | )% | | | 1.43 | % | | | 24.07 | % | | | 23.08 | % | | | (5.88 | )% | Portfolio turnover rate (3) | | | 59.65 | % | | | 129.57 | % | | | 168.67 | % | | | 61.11 | % | | | 7.63 | % | Ratio of operating expenses to average net assets (3) | | | (19.94 | )% | | | (21.73 | )% | | | (10.30 | )% | | | (7.16 | )% | | | (7.27 | )% | Ratio of net investment income (loss) to average net assets (3) | | | (2.25 | )% | | | 5.12 | % | | | 9.89 | % | | | 5.35 | % | | | (5.86 | )% | Ratio of realized gains (losses) to average net assets (3) | | | (3.00 | )% | | | 0.85 | % | | | 31.30 | % | | | 0.05 | % | | | 28.35 | % |
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