For those asking about pensions for our parents and grandparents - although the idea of a state retirement pension started in the early 1900's, the pension system we know was really born after the second world war. Men paid the national insurance contribution, as now, who h allowed them to access unemployment benefits, sickness benefits and retirement pensions at a fixed rate. Single women paid the same. Married women had a choice - they could pay full NI, giving them access to the same benefits as men, or 'married woman's NI', which allowed them to build up a pension, but not other benefits. Women who did not work, could claim a pension from their husbands NI contributions, but only once he had reached pension age and it was a much lower rate. For women who had paid some NI, but not enough for a full pension, they got the higher amount of either their own pension, or what they would have got from their husband's contribution. The married women's NI ceased in the early 1970's, though women who were already paying at that rate, were allowed to continue if they wished. At the time my grandparents married, many employers would not employ married women although ww2 changed that somewhat. Equally, my mum was expected to stop work when I was born, there was no compunction on employers to keep jobs available or pay maternity leave like now. Once things like supplementary benefit came in, retired people could apply for this to top up their pension - it was means tested and was supposed to ensure a basic standard of living.
I imagine that pension credit works similarly?
Also, as some have already said, state pension is dependant on contributions being paid, not the amount of those contributions, so even a part time worker can earn a full pension. My own state pension ( as checked last week) will be almost the same as I currently earn!