We present a revised metallicity distribution of dwarfs in the solar neighb
ourhood. This distribution is centred on solar metallicity. We show that pr
evious metallicity distributions, selected on the basis of spectral type, a
re biased against stars with solar metallicity or higher. A selection of G-
dwarf stars is inherently biased against metal-rich stars and is not repres
entative of the solar neighbourhood metallicity distribution. Using a sampl
e selected on colour, we obtain a distribution where approximately half the
stars in the solar neighbourhood have metallicities higher than [Fe/H] = 0
. The percentage of mid-metal-poor stars ([Fe/H] < -0.5) is approximately 4
per cent, in agreement with present estimates of the thick disc.
In order to have a metallicity distribution comparable to chemical evolutio
n model predictions, we convert the star fraction to mass fraction, and sho
w that another bias against metal-rich stars affects dwarf metallicity dist
ributions, due to the colour (or spectral type) limits of the samples. Reco
nsidering the corrections resulting from the increasing thickness of the st
ellar disc with age, we show that the simple closed-box model with no insta
ntaneous recycling approximation gives a reasonable fit to the observed dis
tribution. Comparisons with the age-metallicity relation and abundance rati
os suggest that the simple closed-box model may be a viable model of the ch
emical evolution of the Galaxy at solar radius.