Final answer:
GDP per capita is the measure used to assess the standard of living in the context of long-run economic growth, as it indicates the average economic output per person, correlating closely with living standards.
Step-by-step explanation:
When assessing long-run economic growth and the standard of living, the most informative measure is GDP per capita. This metric takes the Gross Domestic Product (GDP) and divides it by the population, giving an average value of economic output per person. Using GDP per capita provides a clearer picture of how much value, on average, each individual contributes to and receives from the economy, which correlates with living standards.
Total GDP might reflect the size of an economy, but it doesn't account for population size. The economic growth rate indicates the rate at which an economy is growing, which is important but doesn't provide direct insight into living standards. Inflation rate is a measure of price stability and although important for economic analysis, it doesn't directly inform us about the standard of living.