The FHFA sets affordable housing goals by benchmarking past and predicted future single family and multifamily housing financing volume.
For single family, goals are set based on percentage or overall qualified single-family purchases. The low-income home purchase goal for 2015-17 is 24% and is set to remain at 24% of overall qualified single-family purchases for 2018-20. The very low-income home purchase goal is proposed to remain at 6%. The low-income areas home purchase subgoal is proposed to move from 14% to 15% and the low-income housing refinance goal is proposed to remain at 21%.
The multifamily goals are based on the number of multifamily units financed. The low-income goal for 2015-17 is 300,000 and is proposed for 2018-20 to be 315,000. The very low-income goal is set to remain at 60,000, and low-income small multifamily subgoal (which was 6,000 in 2015, 8,000 in 2016, and 10,000 in 2017) is proposed at 10,000 for 2018-20.
The FHFA announcement and proposed rule can be found here.