I am currently working with panel data, namely its correlations. The data is three-dimensional. I am looking for a way to aggregate the correlation coefficients. I found a model which uses the Fisher transformation to do this as shown as follows:
Let $i$ be an invidual (20), consisting of 5 buckets $b$, each containing its own time-series, $j$, $n_j = 3000$ For example, 20x3000x5.
$\rho_{i,j} = \frac{e^{2z}-1}{e^{2z}+1} $
$ z = \frac{1}{\sum_{ib}^{N}n_{i,b}} \sum_{ib}^{N}n_{ib}(\frac{1}{2} ln(\frac{1+\rho_{ib}}{1-\rho_{ib}})) $
Assume $i$ and $j$ follow bivariate normal and are i.i.d.
Why would this be a legitimate way of aggregating the correlation coefficients, if it is at all?
EDIT:
So there is a financial application actually, there are 20 assets i, each of them has a time-varying standard deviation j so time-series with 3000 observations, but the standard deviations are divided by so called maturity buckets b "up to 30days", "up to 60 days" etc. The n-dimensional array is 20 by 4 by 3000.