  For emitters in a medium, different macroscopic or microscopic theoretical
models predict substantially different dependencies of the spontaneous emission
lifetime on refractive index. Various measurements have been carried out on
Eu$^{3+}$, Ce$^{3+}$ and Nd$^{3+}$ ions, and quantum dots in different
surrounding medial. The dependence of the spontaneous emission rates on
refractive index has been interpreted with different models. By closely
examining some of the experimental results, we notice that some interpretations
are based on implicit assumptions which are hard to justify, and some
measurements contain too big uncertainties to discriminate among different
models. In this work we reanalyse the avilable measured results and give a
consistent interpretation.
