essays in public finance and industrial organization a dissertation ...
essays in public finance and industrial organization a dissertation ...
essays in public finance and industrial organization a dissertation ...
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CHAPTER 3. MEDIGAP 132<br />
policy that could not plausibly be related to the unobserved component <strong>in</strong> the cost<br />
equation. MA penetration decreased over the first part of our sample as policies<br />
enacted <strong>in</strong> the 1997 Balanced Budget Act to reduce Medicare payments <strong>in</strong>directly<br />
decreased MA payments. MA penetration rates were then buoyed up by <strong>in</strong>creased<br />
payments written <strong>in</strong>to the 2003 Medicare Modernization Act (?). In addition, the<br />
goal of MA has shifted over time from promot<strong>in</strong>g efficiency to <strong>in</strong>clud<strong>in</strong>g broader goals<br />
such as regional equity mean<strong>in</strong>g there has been great variation over time <strong>in</strong> federal<br />
policy toward regional MA <strong>in</strong>surers. Thus most of the changes over time were driven<br />
by federal policy that could not be related to the unobservable.<br />
We also statistically test for the endogeneity of the county-year specific MA pen-<br />
etration variables. Recall that our Meidgap choice equation has two sets of excluded<br />
variables: Medigap premiums <strong>and</strong> the MA penetration variables. Based on the as-<br />
sumption that estimates from a specification us<strong>in</strong>g only Medigap premiums are con-<br />
sistent but <strong>in</strong>efficient <strong>and</strong> estimates from a specification with both Medigap premiums<br />
<strong>and</strong> MA penetration are efficient, a Durb<strong>in</strong>-Wu-Hausman test squarely fails to reject<br />
the exogeneity of MA penetration variables. In our preferred specification with the<br />
full set of controls, the test returns a Chi-squared value of 0.8, a value vastly below<br />
the 5 percent critical value of 37.6. Tests run on other specifications yield similar<br />
results.<br />
3.6 Results <strong>and</strong> Discussion<br />
3.6.1 Premiums <strong>and</strong> Medigap Choice<br />
Below we present basel<strong>in</strong>e estimates of the empirical model, start<strong>in</strong>g with the first<br />
stage premium equation, followed by the mult<strong>in</strong>omial logit second stage Medigap<br />
choice equations, <strong>and</strong> f<strong>in</strong>ally the third stage cost equation. Each of these equations is<br />
estimated with three different sets of control variables. A sparse specification <strong>in</strong>clud-<br />
<strong>in</strong>g only key variables <strong>and</strong> year fixed effects; a specification that <strong>in</strong>cludes the demo-<br />
graphic controls; <strong>and</strong> a full specification that, along with the demographic variables,