First look at this figure-
Since 1988, over 1,735+ people have graduated with a UK PhD in archaeology. I must emphasis the plus (+) as this is the bare minimum number. The data is taken off of the Research Assessment Exercise (RAE) which relies on self reporting. Most universities that offer a archaeology PhD respond but the coverage is not 100%, for example the University of Edinburgh did not respond to the 2008 RAE and the University of Manchester was missing from earlier ones. This means there is a slight under reporting in numbers.
Considering the only job that a PhD is need for in archaeology is a University lectureship(lecture, senior lecture, reader, professor, etc.) or research position there are a lot of potential candidates for those positions. Are there enough jobs?
Roughly 440 archaeology lectureships are in the UK currently. For the last decade we have been pumping out about 100+ new PhDs each year. Assuming a natural job span of 30 years and a even distribution we would be looking at around 15 new positions become available each year through retirements, about 7 new PhDs each year for ever position.
Basically, 6 out of every 7 new PhDs would have gotten a degree that will not provide them with any future job benefits. Not everyone gets a PhD to become a Lecturer but the majority do, which means a lot of time and money squandered.
This concept, not enough academic jobs, is nothing new but the hard numbers are. If you are looking to become a Lecturer weight your options carefully.