The impact of HMO penetration on the relationship between nurse staffing and quality.

While there are a number of studies examining the relationship between nurse staffing and quality, none has examined structural differences in the relationship between nurse staffing and quality contingent upon the level of managed care penetration. We used administrative data, and a dynamic panel data model to examine this relationship in a panel of 422 acute care hospitals from 1990 to 1995. We found that there were significant differences in the relationship between nurse staffing and both mortality and length of stay depending upon the level of HMO penetration in the hospital's market.