About fifteen years ago, my "financial advisor" had access to a Morningstar program that took all of my my mutual funds holdings--in me and my wife's retirement accounts, our taxable fund portfolio and, at that time, my children's 529 accounts. The program aggregated the total shares that we had in each company, across all of the mutual fund shares that we owned--from many thousands of shares in S&P 500 companies, to literally a couple of shares in some obscure companies that I had never heard of. The program then rank-ordered each company's shares by the value of the shares that I had in each company. The paper print-out was huge; maybe three feet long. There must have been a total of 300+ different company stocks on the list.
It was a very interesting exercise. One thing that it showed me was that, although diversification of holdings works on the level of mutual funds, spreading assets across mutual funds really doesn't add much--if anything--in diversification of company holdings. If you hold shares in 20 mutual funds rather than 5 mutual funds, you may just end up holding a lot of shares in the same corporations; those shares are just held in different mutual fund "wrappers."
Is this disaggregation/rank ordering technique available today? I would be interested in seeing just how my mutual fund holdings are spread among different companies.