This is a similar question to this one (which has unfortunately no answer yet), although I believe my question is more specific.
Let $X$ and $Y$ be two discrete random variables with outcome space, respectively, $\mathcal X$ and $\mathcal Y$. Then, the mutual information between $X$ and $Y$ is
$$I(X,Y) = -\sum_{x\in \mathcal X, y\in \mathcal Y}p_{X,Y}(x,y)\log \left(\frac{p_{X}(x)p_Y(y)}{p_{X,Y}(x,y)}\right),$$
where $p_X$ is the marginal pmf of $X$ and $p_{X,Y}$ is the joint distribution of $X$ and $Y$. The lower bound of the mutual information is zero, which occurs if and only if $X$ and $Y$ are independent. The upper bound of $I(X,Y)$, on the other hand, cannot exceed the entropies of either $X$ nor $Y$. So,
$$I(X,Y)\le \min\{H(X),H(Y)\},$$
where $H(X) = - \sum_{x\in \mathcal X} p_X(x)\log p_X(x)$.
Because of the variable upper bound of $I(X,Y)$, a normalized version of the mutual information is often used in research on, say, clustering comparisons. The most often used normalied versions that I've encountered are
$$ I_{AM}(X,Y) = \frac{I(X,Y)}{\frac{1}{2}[H(X)+H(Y)]} \quad \text{and}\quad I_{GM}(X,Y) = \frac{I(X,Y)}{\sqrt{H(X)H(Y)}}.$$
But
$$\min\{H(X),H(Y)\}\le HM(H(X),H(Y)) \le GM(H(X),H(Y)) \le AM(H(X),H(Y)) \le \max\{H(X),H(Y)\}$$
with equality if and only if $H(X)=H(Y)$, where $HM, GM$, and $AM$, respectively, stand for the harmonic, geometric, and arithmetic mean. So, the harnomic mean between the entropies would give us a tighter upper bound on the mutual information. I was wondering whether there is a specific reason why the geometric and arithmetic means are preferred for normalizing the mutual information.
Any suggestions would help. Thanks!