different forecasts in different Economic Calendars

Hi everybody
I have recently noticed that Economic Calendars forecast different numbers for an event
so I really wonder if anyone have information about their sources.
which calendar we can trust more?
there are lots of them like myfxbook , fxstreet,forex live and...
and as you know for some important events we see y/y and m/m in other calendars but in forex factory there is m/m or y/y
so it is important we know about major sources that they get these numbers
All the best

As far as I know, some of them use http://www.consensuseconomics.com/ and others use Bloomberg for their forecasts.

Just use bloomberg, they are the best and their economic calenders are spot on..

by bloomberg you mean this http://www.bloomberg.com/markets/economic-calendar/
why it does not cover other countries events?

Well, which source does ForexFactory use? Bloomberg or Consensuseconomics?