For many of us, the New Year is a reason to celebrate. The new calendar is welcomed with parties, fireworks and even a ball drop. But a very different kind of countdown is coming to the business world in 2020. That's when the 80 million millennials (ages 18-31) are estimated to make up 50 percent of the employee population.

Whether this milestone is celebrated or not will depend on how well your company is prepared for this demographic change. I recommend businesses create strategies in advance of this historic shift to make sure they are prepared for the opportunities and challenges to come. Here are five things for companies to consider in 2015 so that they are more than ready for the big Gen Y countdown.