Over the years MU have usually had at least one major rival (MC, Chelsea, Arsenal) and when they play away to that team they are usually not the favourite unless there is some mitigating circumstance (dead rubber, serious injuries/suspensions, or atrocious form from the other side). As a rough rule of thumb when there is a 'balanced' fixture it will give odds at around 2.7 per side which isn't far below 2/1 so it doesn't take much of an imbalance to push the underdog up to 2/1. And when Chelsea and Arsenal were in their pomp in the noughties they were usually the favourites when playing at home (don't forget from 2002-5 for example that Man United only managed a top 2 finish once in four seasons).
edit: heck even teams that aren't their major rival can still push the odds to 2/1 - if you look at Chelsea vs MU from this season for example Chelsea were 6/4 compared to MU at 2/1.
In summary I would be amazed if MU haven't been 2/1 or higher in a minimum of at least one league fixture in the majority of seasons in the past 15 years. Only thing that might skew it is if you go back more than 10 years ago there was less competition in the betting market (no betfair and very limited online betting, comparison sites etc) so available odds were probably slightly less favourable.
...that is ridiculous!
....I have done all 4 games to be draws today. Wimbledon vs Mk Dons was 1-1 and Burnley Blackurn was 0-1 both with a minute or two to go.....Burnley equalize and then literally seconds later Wimbledon socre
