Analysis of the Joint Distribution of Disproportionate Share Hospital Payments. Low-Income Patient Shares

09/01/2002

We examined the relationship between the proportion of low-income patients by payer to address the question of whether one of the more readily available statistics, e.g., the percentage of Medicaid days, is an appropriate proxy for a hospital's percentage of low-income days. We combined Medicare SSI and Medicaid days into a measure of "joint" days and we also computed the patient percentage used in the current Medicare DSH formula (Table 7.2). We found the percentage of Medicaid days is highly correlated with the percentage of low-income days (0.920). The correlation using "joint" days is lower (0.862). Self-pay and no-charge days are poorly correlated with either Medicaid days alone or the "joint" days. The correlation between the DSH patient percentage and the proportion of low-income days is 0.838.

Table 7.2 
Proportion of Low-Income Patients By Payer: 
Hospital-Weighted Means and Correlation Between Measures
  % Medicare SSI % Medicaid Days % No-charge + self-pay days % Joint days % Low-income days DSH Patient %
MEAN 0.042 0.129 0.044 0.171 0.176 0.215
STD 0.045 0.118 0.054 0.136 0.141 0.183
N 638 638 638 638 638 638
Pearson's Correlation Coefficient**
% Medicare SSI 1.000 0.237 -0.014 0.538 0.193 0.579
% Medicaid Days   1.000 0.160 0.946 0.919 0.912
% No-charge/self-pay days     1.000 *0.134 0.520 *0.145
% Joint days       1.000 0.862 0.984
% Low-income days         1.000 0.837
DSH Patient %           1.000

* p<.001; ** except as noted, all values p<.0001


We also explored the relationship between the different types of measures of the hospital's care to low-income inpatients. In Table 7.3, we report the correlations between the hospital's percentage of Medicaid and all low-income patient days, discharges, and inpatient charges. The hospital's proportion of Medicaid inpatient charges is highly correlated with its Medicaid discharges (0.955) and Medicaid days (.950). Compared to its average proportion of inpatient days (.129), Medicaid has on average a higher proportion of discharges (.147) and lower proportion of inpatient charges (.110). The large number of Medicaid maternity cases probably accounts for the differences. The same pattern is seen in the overall measures of care provided to low-income patients.

Table 7.3 
Different Measures of Low-Income Inpatient Care:
Hospital-weighted Means and Correlation Between Measures
  Medicaid
Days
Low-income
days
Medicaid
discharges
Low-income
discharges
Medicaid
charges
Low-income 
charges
MEAN 0.129 0.176 0.146 0.237 0.109 0.193
STD 0.118 0.141 0.125 0.159 0.101 0.139
N 638 638 638 638 638 638
Pearson's Correlation Coefficient**
Medicaid Days 1.000 0.919 0.917 0.849 0.949 0.840
Low-income days   1.000 0.836 0.898 0.879 0.888
Medicaid discharges     1.000 0.906 0.955 0.843
Low-income discharges       1.000 0.894 0.965
Medicaid charges         1.000 0.894
Low-income charges           1.000

** all values p<.0001

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