  We study integrated characteristics of ~14000 low-redshift (0<z<1) compact
star-forming galaxies (SFGs) selected from the Data Release 12 of the Sloan
Digital Sky Survey. It is found that emission of these galaxies is dominated by
strong young bursts of star formation, implying that their luminosities
experience rapid variations on a time scale of a few Myr. Reducing integrated
characteristics of these galaxies to zero burst age would result in a
considerably tighter and almost linear relation between stellar mass and star
formation rate (SFR). The same correction implies that the specific star
formation rate (the ratio of SFR and stellar mass) is not dependent on the
galaxy stellar mass. We conclude that the correction for rapid luminosity
evolution must be taken into account in a similar way when comparing different
samples of low- and high-redshift SFGs. If the bursting nature of star
formation and young burst ages are characteristics of the galaxies selected at
high redshifts, the age correction of observed SFRs derived from the Hbeta
emission line or UV continua would modify the derived SFR densities in the
early universe.
