Hi Jim,
I believe that the FCC licenses no more than 12.5 kHz channel spacing unless you meet the "equivalent efficiency" standard.
This is not my area of expertise. My basic understanding is that as channel width increases, so does max data rate. With a base transmission rate of 1 Hz we aren't filling the 25 kHz channel spacing (or even the 12.5 kHz spacing). If we can prove that we are transmitting at least 4.8 kbps per 6.25 kHz channel (19.2 kbps per 25 kHz channel) then our efficiency (filling the channel) is equivalent to using lower data rates with smaller channel widths.
Essentially the regulators don't want us to occupy a large pipe with a tiny flow rate. If we can prove the pipe is full, then they might allow the increase.