Good references were indeed essential to finding work as a servant. You might be interested in my response to the question: What venues were most common for hiring house servants?

I'm guessing it's pretty accurate, although I don't know if the ratio of good/bad/no, references or people's trust in them was really so dramatic.. Everyone in the house is so obsessed with making sure a servant has good references before working with them and they seem so shocked and betrayed when the references deceived them. And yet the family and Mr. Carson / Mrs. Hughes hand out good references like candy. There's only one person who doesn't get a good reference when they leave Downton (Ethel) and the whole cast seems to attempt to "correct" that decision for years afterwards 😅 It's funny that anyone takes references seriously when they know exactly how rare a bad (or no) reference is, regardless of the sin or, often times, crime of a servant.