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I would put "internal combustion engine" in place of "automobile" since the one subsumes the other, and since diesel locomotives are a twentieth century thing even with rail grids being transitional, nineteenth-twentieth century phenomena. Think also, the first steel hull vessels were the Civil War Confederate and Union efforts; and merchant steel hulled vessels [now including tanker and container economies of scale] all are twentieth century developments. It was horse and buggy before the internal combustion engine, and while steam was important as a direct power source previously, it now finds use primarily to drive turbines in power plants and nuclear warships. Petroleum and internal combustion have dwarfed civilian steam and water power except for electrification. With the electric automobile set to displace petroleum personal transit use, and with peak oil likelihoods now or soon, conservation of liquid fossil fuel will be the rule. Hence, can anyone dispute electrification as leading the list? Rolling air conditioning and refrigeration, and household appliances into "electrification" would make sense, except then making twenty items would involve looking beyond the published listing. Indeed, X-ray or CAT scan me without the power grid -- that thinking then makes electrification even a bigger thing since the other healthcare innovations (aside from direct power consumption hospital tools) depend upon electrification in manufacturing stages. Perhaps "polymers" and other chemistry - chemical engineering innovation should be listed. As with electrification, materials science and pharmaceuticals reach to all the listed classifications, making it something difficult to list separately. Also, much chemical science and engineering dates to nineteenth century European effort; DuPont and gunpowder, etc.