The $equil_yield table created by the SS_output function in r4ss is from the SPR/YPR_profile in Report.sso. It is used in r4ss primarily to create the yield curve plot where the peak should match the MSY value. It would be useful to add an additional plot related to the Yield Per Recruit estimates.
I believe this table is created by iteratively increasing and decreasing a multiplier on all the fleet-specific F values where the selectivity, biology, recruitment distribution, and allocation among fleets are all determined by the settings in the forecast file under "Benchmarks", "Bmark_years", and "Bmark_relF_Basis".
In Report.sso there is additional information at the end of the table like the following:
Finish SPR/YPR profile
#Profile 0 is descending additively from max possible F: 4.09778
#Profile 1 is descending multiplicatively half of max possible F
#Profile 2 is additive back to Fcrash: 0.210143
#value 3 uses endyr F, which has different fleet allocation than benchmark
#value 4 is Fspr: 0.107403
#value 5 is Fbtgt: 0.0722269
#value 6 is Fmsy: 0.0763359
#Profile 7 increases from Fmsy to Fcrash
#NOTE: meanage of catch is for total catch of fleet_type==1 or bycatch fleets with scaled Hrate
