The property tax bill is calculated as rate × assessed value. In almost every other state, the assessed value is directly proportional to the current fair market value, but in California, Proposition 13 lowered the legal tax rate and also changed the assessed value to be the price that you (or your ancestors thanks to Proposition 58 and 193) originally acquired the property, adjusted for inflation. What this means is that some people pay outdated property taxes that are a fraction of what their new neighbors are paying, while they benefit from receiving market-rate rents or benefit from modern amenities (schools and jobs). The effective tax rate is the property tax amount divided by the fair market value, which allows us to compare fair market tax burdens given the unfair property assessments: https://www.trulia.com/research/prop-13/.

To my point above, property taxes are intertwined with the debate about homeownership because Proposition 13’s low property tax rate increases wealth inequality (since landowners instead of governments capture the value of increased rents), increases wealth inequality (since governments are forced to increase regressive sales taxes and fees instead of property tax), increases wealth inequality (since the US income tax often does not capture increases in imputed rent and capital gains), disincentivizes cities from zoning for more housing (since the property taxes from new housing no longer pays for the infrastructure costs), and encourages NIMBYism (since homeowners have to purchase the land at a high price and then become extremely risk-averse). In addition, Proposition 13’s unfair asssesed value system further encourages NIMBYism (since landlords and homeowners get to benefit from displacing the poor without having to pay any higher property taxes) and encourages long-term property speculation without investment (since long-term property owners have low holding costs despite being in expensive locations). In another state, where homeowners have to pay taxes for the privilege of excluding others, homeownership would not be harmful to society.