Wages since 1971 adjusted

I was doing some back-of-the-napkin calculations on wages in 1975 compared to 2024 and the results were quite remarkable, the minimum wage in NZ in 1975 was $1.95, equivalent to about $22, this compares well to the current minimum wage of $23.15 until we factor in that there has been GDP per capita increase from $4172 ($24318 (USD) in 2024) to $48528 (USD) between 1975 and 2023, this is roughly 2 times the GDP of NZ back in 1975 when adjusted, so if wages were to follow the same trajectory then the minimum wage could be $44 to match growth. I understand that there is a lot more overhead involved in the increased productivity, so not all that extra money should be passed onto the workers, but it is pretty decent proof trickle-down economics is at best a pipe dream. What was more of an eye-opener though was the average wage in 1975 was $4.52, or NZD 51 per hour, compared to the current average of $42.06. If this wage was adjusted, then it should be closer to $102 an hour. I know this is very rushed and the math probably doesn't even make sense, but I wondering what is going on. It seems everyone blames another political party, but this is a trend that both have overseen and never altered. Does anyone have any idea what has caused this?