Jason is correct. When I sent the data to Sean to post I wrote up caveats, but they didn't make it to the Sticky. The chart shows constant disinfecting chlorine levels of 0.03 ppm for the Min FC, 0.05 ppm for the Target FC, 0.07 ppm for the Yel/Mstrd FC (which is similar to Ben's Max column), 0.3 ppm for the Shock FC, and 0.7 ppm for the Yel/Mstrd Shock.
Obviously, you need a certain minimum FC level regardless of the CYA level so at very low CYA levels (probably below 30 ppm CYA) the chart no longer makes sense. As for what that minimum FC level should be, it depends on your pool's chlorine usage and how often you add more chlorine. You want to have enough FC to be there in reserve for a localized "accident" or local algae growth or organic debris (e.g. pollen). Obviously, I can't quantify this, but for an outdoor pool it's probably somewhere in the neighborhood of 2 or 3 ppm FC.
The rough rules I give of 7.5% of the CYA level for Min FC, 11.5% of the CYA level for Target FC, 15% of the CYA level for Yel/Mstrd FC, 40% of the CYA level for Shock FC, and 60% of the CYA level for Yel/Mstrd Shock are very reasonable approximations. You can see that from the chart -- they only fall apart at very low CYA levels near zero.
The chart or approximations work rather well tracking Ben's Min and Max columns, but it doesn't track his Shock column very well. This is because my chart is based on disinfecting chlorine level so will determine the RATE at which chlorine will kill algae so the values in my chart will all kill algae at the same rate. There are two issues, however. At low CYA levels, the lower shock FC levels may "run out". So again there needs to be some minimum FC level for shocking for any CYA level. This depends on the amount of algae there is and how often you add chlorine. I would guess that a minimum of 10 ppm is about right. The other issue is at higher CYA levels. Though I am confident of the chemistry behind using about 40 ppm FC at 100 ppm CYA to shock a pool (for green algae), those with vinyl liners may wince. Also, the CYA test isn't prefectly accurate and when at such high chlorine-to-CYA percentages, errors in CYA have the disinfecting chlorine level swing quite a bit. So using a lower FC of perhaps a minimum of 25% of the CYA level would still kill algae in a reasonable time period, but would do so more slowly than at 40%. Technically, any FC level above the "Min" column will kill green algae faster than it reproduces, but in an algae bloom local FC levels drop a lot so too little FC isn't good.
Finally, the SWG level is a tough one to set since not everyone has success at lower levels though most do. If I were to hazard a guess based on the rough 3 ppm FC at 60-80 ppm CYA that most pools seem to be able to handle to keep away green algae, then I would say that for SWG pools the disinfecting chlorine level for the "Min" which is also a "Target" due to near-continuous chlorine introduction is around 0.02 ppm which translates to an FC level of around 4.3% of the CYA level. We could add another column to the chart where I more accurately calculate the FC numbers, but most people run 60-80 ppm CYA so just saying 3 ppm FC minimum works for most SWG pools (maybe 3.5 ppm FC is better for the 80 ppm CYA pools).
Richard