In established, competitive markets, if a brand's share of advertising spend is greater than its share of market, it is likely to grow (and if its share of spend is less than its share of market, it is likely to decline).

The relationship, does, however, vary by brand size. Big brands can get away with a slightly lower share of spend to share of market ratio to maintain their position whereas small brands often need a higher ratio in order to grow.

What to learn more? Try asking Virtual Dan White.