Originally Posted by forgiven2008
At certain readiness levels your decisions in the final outcome decide if earth is destroyed and so on. Certain things can only happen at certain readiness levels.
2. It is not required to do multiplayer or any phone apps to hit 100% EMS.
edit: How EMS and the "perfect" ending works...
Readiness Rating = Galactic Readiness.
This percentage is multiplied by your Total Military Strength. Your Effective Military Strength is your actual rating.
IE you have a TMS of 3000, but only have a Readiness Rating of 50%, thus your EMS is 1500. Your EMS is what is factored into the games various endings.
Doing Multiplayer or the phone apps will increase your Readiness Rating percentage, meaning you have to do less exploration and farming to achieve max EMS. However you do not need to do MP or the phone apps to max out EMS.