Way, way less than you think. 2+2++1+3%. That is the entirety of food workers and food transportation, packaging, and sales, respectively, as a percentage of population for the united states, which produces twice the food needed by the population.

Water workers? maybe 5%. and that's a hard maybe because that includes all plumbers, not just infrastructure. Electricity? As long as we don't go with coal and oil it's an average of 1 worker per GW. admittedly line workers and electricians make up a decent chunk approaching 3 whole % of a population, but let's be honest here, we're fine on that front still.

And that's the great thing about economies of scale and automation and mechanization. It's not the 1700s anymore. We don't have to have 98% of the population in food production. We don't have to waste productivity. We are, and this isn't a joke, on average more than 10,000 times more productive as individuals and as a species than our ancestors.