23(40)
Tabell 4.
Tooth extraction vs. Basic examination & diagnostics,
performed by dentist.
(1)
(2)
(3)
Interaction: K*competition1km
Elasticity
-0.00899*** -0.00899*** -0.00899***
Standard error
(0.000942)
(0.00258)
(0.00258)
Constant
6.713
6.762
6.667
Clinic FE
No
Yes
Yes
Time dummy
No
No
Yes
0.631
0.785
0.826
adj.
0.631
0.753
0.800
15,864
15,864
15,864
Standard errors are clustered at the clinic level and the pooled model is estimated
with a public clinic dummy. All regressions are weighted with the number of patients
at each clinic per year.
***
p
< 0.001
6.2
Sensitivity analyses
To test the results sensitivity to the choice of services, the models have
been estimated with examinations performed by either dentists or dental
hygienists as the first-stage service and all other services in the register
as follow-on services.
27
The elasticities are negative and statistically
significant, falling in the range -0.019% to -0.022%. This indicates that the
main results reported above are not an artifact of the choice of services.
Furthermore, in order to test the sensitivity of the results to functional form
the same models have been estimated in levels instead of logs. This does
not change the inference from the log-log estimates; the elasticities are
negative and statistically significant. Results from these estimations are
given in the appendix, table B1–B5.
As a further sensitivity analysis, I re-estimate the models using clinics
within five kilometers as a measure of competition. The point estimates
are smaller, but the results do not change qualitatively. When adding a
clinic fixed effect and year dummy the results are no longer statistically
significant. The results are given in table 5.
27
Estimation with and without fixed effects for time and clinic.
