Final answer:
The rate of market share growth decreases when the market share has already exceeded the outlet share and continues to increase. This is due to diminishing returns in a saturating market.
Step-by-step explanation:
When considering the relationship between market share and outlet share, once a company has achieved a market share greater than its outlet share, any further increase in outlet share typically affects market share growth. According to the concept of diminishing returns, beyond a certain point, each unit increase in outlet share will contribute less and less to market share growth. Specifically, the correct answer to this question is that the rate of market share growth decreases with a further increase in outlet share. This is because the market is likely becoming saturated, the most receptive consumers have already been reached, and there are fewer new customers to gain from additional coverage.