  We present an analysis of correlations between integrated properties of
galaxies and their populations of young massive star clusters. Data for 21
nearby galaxies presented by Larsen & Richtler (1999) are used together with
literature data for 10 additional galaxies, spanning a range in specific U-band
luminosity T_L(U) from 0 to 15. We find that T_L(U) correlates with several
observable host galaxy parameters, in particular the ratio of Far-Infrared
(FIR) to B-band flux and the optical surface brightness. Taking the FIR
luminosity as an indicator of the star formation rate (SFR), it is found that
T_L(U) correlates very well with the SFR per unit area. A similar correlation
is seen between T_L(U) and the atomic hydrogen surface density. The cluster
formation efficiency seems to depend on the SFR in a continuous way, rather
than being related to any particularly violent mode of star formation. We
discuss fundamental features of possible scenarios for cluster formation. One
possibility is that the correlation between T_L(U) and SFR is due to a common
controlling parameter, most probably the density of the ISM. Another scenario
conceives a high T_L(U) as resulting from the energy input from many massive
stars in case of a high SFR.
