Graphs · Decline curve
Global Sperm Concentration, 1973–2018 (with trend projection)
Line chart with projection
Solid line is the measured 1973–2018 series. Dashed line in oxblood extends the established 2.3-percent annual decline forward as a projection if the trend continues.
Projection with uncertainty band
Same trend and projection, plus an illustrative confidence band on the projected portion. The band widens forward in time to reflect compounding uncertainty.
Decade averages
Mean concentration per decade (measured data only). Coarser view of the same decline.
Source: Levine et al. 2023 · Human Reproduction Update
Methodology note: Compiled from Levine et al. (2023), a systematic review and meta-regression of 223 sperm-concentration studies covering 1973–2018, published in Human Reproduction Update. The paper reports a biphasic decline with the post-2000 rate roughly 2.17× the pre-2000 rate. The curve here applies that acceleration ratio at rates of 1.09%/yr (1973–2000) and 2.36%/yr (2000–2018), scaled so the model lands at the paper's reported 2018 endpoint of 49.0 M/mL (the paper's published rounded rates of 1.16% and 2.64% compound to ~45.5, slightly below the reported endpoint due to rounding). The shaded band on the projection portion is illustrative, widening from ±15 percent at 2019 to ±25 percent at 2050. The WHO 2010 lower reference limit (5th percentile of fertile-male distribution) is 15 M/mL.
Raw data: global-sperm-count.json