Weaker, also if you look at the same source with a graph of 2005-2021 you will see that it's going down faster for below-poverty-level the most (bringing them closer together, 95/70/45 in 2005 to 72/60/46 in 2021). I also don't think it's a coincidence that the peak of this graph (before it starts falling for all-but-the-richest) is in 2008.
But also I think this data would probably look different if people living in multi-generational households (or otherwise having family who provide free childcare) was taken into account (which is to say that people aware they have no support will be more reluctant to have kids). On a different note, income alone is leaving out other important factors like the cost-of-living/housing in their area.