As discussed in our press release last night, the company recorded net income attributable to UHS per diluted share of $4.04 for the year and $0.98 for the quarter. After adjusting for a reduction in malpractice reserves relating primarily to prior years, our adjusted net income attributable to UHS per diluted share for the quarter ended December 31, 2011, was $0.91.
Included in the quarter is a year-to-date reduction to our effective tax rate due to final implementation of certain state income tax planning and the securing of certain state tax credits.
We define operating margin as operating income or net revenue less salaries, wages, and benefits, other operating expenses, supplies expense and doubtful accounts divided by net revenue. Our operating margins increased to 16.7% during the quarter ended December 31, 2011, as compared to 15.7% during the comparable prior year period.
On a same-facility basis, revenues in our behavioral health division increased 6.3% during the fourth quarter of 2011. We note that the PSI facilities are included in our same-store data for one month this quarter. Adjusted admissions and patient days to our behavioral health facilities owned for more than a year increased 8.3% and 4.1% respectively during the fourth quarter. Revenue per adjusted patient day rose 2.4% during the fourth quarter of 2011 over the comparable prior year quarter.Operating margins for our behavioral health hospitals owned for more than a year increased to 24.7% during the quarter ended December 31, 2011 as compared to 22.6% during the comparable prior year period. On a same-facility basis in our acute division, revenues increased 1.6% during the fourth quarter of 2011. The increase resulted primarily from a 1.3% increase in revenues per adjusted admission. Adjusted admissions to our hospitals owned for more than a year were relatively flat. The relatively muted revenue growth reflects a $6 million reduction in the quarter of Medicaid disproportionate share and UPL reimbursements, primarily related to Texas as well as the continued impact of negative economic trends in certain of our local markets.