  The measurements of the Hubble parameter using the cosmic microwave
background radiation appear to be inconsistent with the measurements of this
parameter using Cepheid variable stars. This inconsistency may be a result of
using the $\Lambda$CDM cosmology, which assumes pressureless dark matter, in
extrapolating the data from the recombination time to the present time. We show
that both measurements are consistent if dark matter satisfies an equation of
state in which the pressure $p$ and the energy density $\epsilon$ are related
by $p=w\epsilon$ with a negative value of $w$. The data give $w\approx -0.01$.
The negative value of $w$ indicates that dark matter would not be formed by
particles, which is consistent with the lack of experimental evidence for them.
