Ad spend remains one of the biggest and most strategic resource allocation decisions that the management of any leading consumer marketing company has to make. So the speed of change in the world of media and advertising is creating new uncertainties in the executive suite.

The good news is that the rules have not changed, and the questions to be answered remain the same: What do I need to spend in each medium to make sure I get the reach I want? How do I allocate that spend within each medium? And how do I know if it’s working well enough, so I can make changes that will improve it? Similarly, the basic equation for advertising effectiveness hasn’t changed: the more of your ideal audience you can reach, and the more intensely your advertising resonates with them, the stronger your brand lift or sales lift – or reaction. Essentially, reach x resonance = reaction.

Some changes, of course, matter very much. Three of the most important are the fragmentation of media, the rise of Big Data, and innovation in measurement and analytic tools.

For complete insight into these changes, download the premier issue of Nielsen’s “What’s Next.”