I saw an interesting article in the WSJ that sourced it from FRANdata which said:

Franchises with the highest rates of transfers was:

1. Personnel services 8.2%
2. Services-general 7.2
3. Lodging 6.4
4. Fast food 6.1

Franchises with the lowest rates were:

1. Security related .1%
2. Party-related .5
3. Video .9
4. Computer related 1.4