The 2017 online tax lien auction for Pinal county in northern AZ ended 2 weeks ago and here are some unofficial results. Results can change if investors do not make their final payments for their lien purchases.

Average winning interest rates inched slightly higher compared to the last two years, and the number of winning investors grew to 81 from 68 the previous year.

I eliminated the "Struck to County" liens which are the liens nobody bid on and are now held by the county. There were 5,409 liens that were struck to the county. A total of $ 2,731,090.77 in liens not sold.

Number of liens sold to investors:

2017 - 2,505
2016 – 2,301
2015 - 2,713
2014 - 4,931

2013 - 4,340

Total dollar of liens sold:

2017 - $2,943,103.63
2016 - $2,549,429.59
2015 - $2,620,894.70
2014 - $6,831,424.55
2013 - $6,791,144.22

Average rate of return overall:

2017 – 5.84% (10.73% if you include the Struck to County which all get 16%)
2016 - 5.33% (10.74% if you include the Struck to County which all get 16%)
2015 - 4.25% (9.62% if you include the Struck to County which all get 16%)
2014 - 8.38% (11.14% if you include the Struck to County which all get 16%)
2013 - 9.86%

Number of Investors who won liens:

2017 - 81
2016 - 68
2015 - 64
2014 - 99
2013 - 199

Total Number of bids for all liens:

2017 – 11,220
2016 - 11,325
2015 - 15,166
2014 - 20,802
2013 - 48,418

You bid down the interest rate in 1% increments from 16% down to 0%.
Rate that had the most number of bids overall:

2017 – 5% 2,584 bids
2016 - 6% 1,601 bids
2015 - 4% 3,282 bids
2014 - 5% 5,543 bids
2013 - 7% 20,191 bids

Most bids per lien/parcel:

2017 – One lien had 21 bids
2016 - Two liens had 17 bids
2015 - Two liens had 23 bids
2014 - Four liens had 24 bids
2013 - Two liens each had 179 bids

Results by Property Use Type minus the Struck to County (click on image to make larger):