T-Mobile CTO Neville Ray told the FCC his 600 MHz band 5G would be 19% more efficient than LTE. That's the primary 5G band T-Mobile is using across the country. In the 2500 MHz Sprint band, the increase is 52%. (Chart at left and larger below.) It is possible these numbers will prove lower in actual test. Over 80% of the 5G being deployed around the world is low and mid-band. Generally, this is 4G hardware with NR software, with speeds closer to 4G than to 5G millimetre wave. Sprint & T-Mobile will be 90%+ low and midband, little faster than LTE.
Millimeter wave, which Verizon is deploying widely, is about three times faster than LTE in the real world. See Verizon 5G: "I'm getting speeds of 900+ Mbps downstream 200+ upstream." AT&T is deploying mmWave to hotspots in dense urban areas, but intends low and mid-band for most of the country.
Why are so many claiming 5G is five and ten times faster? Many don't realize that most "5G" since the 3GPP Great Renaming in Spring 2018 is now 4G hardware with 5G NR software, not particularly fast. Actually, the majority of 5G is mid-band, 60% to 80% slower than mmWave and not very much better than LTE. Others use out of date LTE capabilities; since 2017, "Gig LTE" is delivering speeds usually between 100 and 400 megabits. (It's more than a gig in the lab, hence the name.)