Bigamy - how common?

[Wiggy]

Thanks Guy!   

[lizdb]

In my researching experience, bigamy is not at all common.  Dont get me wrong I'm sure it went on, but it is somethng I have rarely come across, and indeed have not found any incidence in my trees.
Sometimes at first glance it appears that a marriage maybe bigamous, but deeper research has revealed that there was a death of first wife, or the marriages in question are actually two different people with similar names and occupations, or some such other explanation.

I remember when I first started more serious Family History research, about 30 years ago, having dabbled a bit before then, I went to an evening class. One thing that stuck in my mind was when the lady taking the class said that as we got into our research she would guarantee that it wouldnt be long before we came across illegitimacy, and that as we went further she would be pretty certain we would encounter the workhouse, someone in prison, a lunatic, someone emigrating, plus come across a time when some branch of the family had a non-conformist phase.   Bigamy wasnt on her list of things! 
Sure enough as time has gone by we have found incidences of all these things, but none of bigamy.

[Galium]

It is probably more usual to find couples living as man and wife, where one (or both) parties is already married to someone else. If both of them know of the existing marriage/s, there wouldn't be much point in going through a marriage ceremony which both know to be invalid. 
Bigamy is most likely to be where the party who is not previously married doesn't know that their bride/groom isn't free to marry them.

Until the Divorce Reform Act of 1971, someone who wished to end their marriage, and be free to re-marry  would be unable to do so unless their spouse (the 'innocent' party) agreed to petition for divorce - this might account for someone not getting a divorce if they left their spouse in the 1960s.

[chris_49]

I too find couples living together (often pretending to be married) more common than bigamy. Though both were an option, only bigamy was a crime in the UK ("fornication" illegal in many US states?) so co-habitation was the safer option. Nearly always, one partner being already married was the reason.

I didn't find a couple openly cohabiting until the 1911. They are self-described as such, with separate surnames. The children were registered under her surname, but they seemed to have fooled the vicar - they were baptised under their father's name!

[Guy Etchells]

I too find couples living together (often pretending to be married) more common than bigamy. Though both were an option, only bigamy was a crime in the UK ("fornication" illegal in many US states?) so co-habitation was the safer option. Nearly always, one partner being already married was the reason.

The reason for that was co-habitation was a form of marriage in the UK.
The different countries in the UK repealed such "common-law" marriage at different times with Scotland being the last in 2006.
Cheers
Guy