Discuss the relevance of the Growth-Share Matrix in portfolio planning.

The Growth-Share Matrix is highly relevant in portfolio planning as it aids in strategic decision-making and resource allocation.

The Growth-Share Matrix, also known as the Boston Consulting Group (BCG) Matrix, is a strategic planning tool that allows companies to visualise their product portfolio and make informed decisions about where to invest, divest or develop products. It is based on the idea that a company’s business units can be classified into four categories based on combinations of market growth and market share relative to the largest competitor. These categories are: stars, cash cows, question marks, and dogs.

Stars are units with high market share in fast-growing industries. They require heavy investment to maintain their growth, but can also generate substantial revenues. Cash cows are units with high market share in slow-growing industries. They require less investment and generate more cash than they consume. These are often the corporation's primary source of cash and are specifically important for portfolio planning.

Question marks are units with low market share in fast-growing industries. They consume resources and generate little cash, but have potential to become stars. Dogs are units with low market share in slow-growing industries. They neither generate nor consume a large amount of cash. Companies usually opt to divest these units.

The relevance of the Growth-Share Matrix in portfolio planning lies in its ability to help companies understand their product mix and identify growth opportunities. It provides a framework for allocating resources among different business units and helps in formulating strategies for growth, based on the market attractiveness and the company's strength.

Moreover, the matrix helps companies to balance their portfolio. For instance, the cash generated from 'cash cows' can be used to fund the 'question marks' and 'stars'. This strategic balance allows companies to safeguard against future uncertainties, ensuring that they have products at every stage of the product life cycle.

However, it's important to note that the Growth-Share Matrix has its limitations. It assumes market growth rate is a proxy for market attractiveness and relative market share is a proxy for competitive advantage, which may not always hold true. Despite these limitations, it remains a valuable tool in portfolio planning.