  Both coronal holes and active regions are source regions of the solar wind.
The distribution of these coronal structures across both space and time is well
known, but it is unclear how much each source contributes to the solar wind. In
this study we use photospheric magnetic field maps observed over the past four
solar cycles to estimate what fraction of magnetic open solar flux is rooted in
active regions, a proxy for the fraction of all solar wind originating in
active regions. We find that the fractional contribution of active regions to
the solar wind varies between 30% to 80% at any one time during solar maximum
and is negligible at solar minimum, showing a strong correlation with sunspot
number. While active regions are typically confined to latitudes
$\pm$30$^{\circ}$ in the corona, the solar wind they produce can reach
latitudes up to $\pm$60$^{\circ}$. Their fractional contribution to the solar
wind also correlates with coronal mass ejection rate, and is highly variable,
changing by $\pm$20% on monthly timescales within individual solar maxima. We
speculate that these variations could be driven by coronal mass ejections
causing reconfigurations of the coronal magnetic field on sub-monthly
timescales.
