How much did the average solitary diamond engagement cost in 1970?

Your answer depends on the cut, colour , clarity and carat weight of the 'average' diamond, and includes the 'average' amount of money the 'average' buyer paid for an engagement ring.

By 1970, the adage -- two months' salary -- was a good guideline offered to buyers of engagement rings: the number of buyers who followed this advice is not clear.