My comment
Subject of MDM is the management of all master entities and the relationships among them as well as with other non-master entities, since the commercial value of MDM is derived from the relationships (roles). ...
An insurance company like your organization that covers Life, General and Health Insurance will need to consider the following master data entities
* Party (natural person or legal entity, but also social group such as household) with their roles "policy owner", "insured person", "injured person" etc.
* Thing (any tangible or non-tangible object, e.g. your products, but also cars, houses) with their roles "policy product", "insured object", "claim object" etc.
* Location (physical or virtual place) with their roles "insured address", "claim location" etc.
The above examples show that MDM in an insurance company is quite complex if you want to profit from it to the maximal extent. Since MDM in any established insurance company is a multi-year integration endeavor that will affect (almost) each and every department, I recommend to develop a plan for the best individual economical approach (cost of inaction, return on investment) to stepwise cover your organization's application landscape.
My additional comment
The duplication of master data should of course be avoided.
In the ideal case, master data are managed by a central application, and all operational applications directly create and update master data using an API of that central MDM application (hub architecture style: "Transaction"), but this is also the most ambitious solution.
Since it will not be possible (and is not recommended) to reorganize all operational applications in one project, your organization will need to develop the already mentioned stepwise approach. During the interim period, it may be necessary to keep master data redundant in the legacy applications and the evolving central MDM application.
However, what will be the best economical solution (i.e. which hub architecture style will best resonate with your organization), can only be found via an individual analysis and business modeling (data, data flows and processes) of existing and potential future applications. For a quick overview of the principal architecture styles for the MDM hub, I recommend you to check out this page: http://datamanagement.manjeetss.com/page/2
