Recent results have suggested that the density of baryons in the Universe , \Omega _ { { B } } , is much more uncertain than previously thought , and may be significantly higher .
We demonstrate that a higher \Omega _ { { B } } increases the viability of critical-density cold dark matter ( CDM ) models .
High baryon fraction offers the twin benefits of boosting the first peak in the microwave anisotropy power spectrum and of suppressing short-scale power in the matter power spectrum .
These enable viable CDM models to have a larger Hubble constant than otherwise possible .
We carry out a general exploration of high \Omega _ { { B } } CDM models , varying the Hubble constant h and the spectral index n .
We confront a variety of observational constraints and discuss specific predictions .
Although some observational evidence may favour baryon fractions as high as 20 per cent , we find that values around 10 to 15 per cent provide a reasonable fit to a wide range of data .
We suggest that models with \Omega _ { { B } } in this range , with h \simeq 0.5 and n \simeq 0.8 , are currently the best critical-density CDM models .