The characteristic pattern of a PE fund's cumulative net cash flow (or NAV): deeply negative in Years 1-2 as capital is called and fees are paid before investments mark up, inflecting positive as portfolio companies appreciate and distributions begin, traced over time as a J-shape. Implications: (i) Year 1-2 IRR is not informative; (ii) interim performance comparisons must distinguish genuine underperformance from the early J-curve trough; (iii) subscription credit lines have flattened the early J-curve by deferring LP capital calls — at the cost of artificially inflating reported IRR by 100-200 bps.