Continuing the series today we look at pass defense. I will take a slightly different approach on pass defense. I will list the top three and bottom three teams for 2018. This is then followed by the three most improved and declined from 2017 to 2018. These are all for pass defense only.
To rank the teams by pass defense I used three statistics:
- Opponent Passer Rating differential
- Opponent Yards Per Pass Attempt differential
- Defensive Quarterback Hits
The differentials are how the opponent fared in that statistic in the game against the team compared to their season average. So if a team had a quarterback rating for the season of 80 and had a game rating against a team of 70 their passer rating differential is -10. A negative differential is good for the defense. I summed those differentials on a per game basis for each team to get a total season differential. For the team’s pass defense a large negative number is very good.
The quarterback hits were not available on a per game basis. So I simply used the sum of a team’s defensive quarterback hits for the season.
To get an aggregate defensive number I summed the team’s standard deviation from the average for each category. The differentials that were negative are better. On the quarterback hits the positive (deviations above the average) were better so I added the negative of the hits deviations. In addition I only take half of the deviation value for quarterback hits. This is to give credit for a strong pass rush but to not overwhelm the other two statistics with the pass rush. I then ranked the teams with the largest negative sum ranking as number one. I then did the same for the 2017 season and got their rankings for that season.
Here are the outlying 10% of teams starting with the best and worst in 2018. This is followed by the most improved and declined from 2017 to 2018 all in pass defense only. I discuss a little about their ranking and then look as where the team stands looking forward into 2019. For looking forward I note any key departures and acquisitions.
Top Three Teams 2018
1. Baltimore Ravens
When playing the Ravens opposing quarterbacks in total performed at a -253.7 passer rating difference from how they averaged for the year. This was the second best defensive passer rating differential. Only three opposing quarterbacks performed above their team quarterback yearly rating. Seven quarterbacks had a passer rating of 20+ points less than their average. Their opponent yards per attempt summed out to a -22.5 differential which was the best by -7.5 yards. Four teams had a greater than -3 yards per passing attempt from their yearly average. They held Phillip Rivers to 181 yards passing , zero passing touchdowns and had two interceptions and four sacks. They were the only team in 2018 to hold the Chargers to under 20 points.
The Ravens acquired free safety Earl Thomas in free agency. In his nine year career Thomas has averaged 4 interceptions and 9 passes defended per 16 games. In playing just 4 games last year due to injury Thomas still had 3 interceptions and 5 passes defended. That should more than offset the release of All-Pro safety Eric Weddle.
2. Chicago Bears
The Bears had the top negative passer rating differential by opposing quarterbacks with a – 291.2. In week 14 they held the Rams to 6 points with zero touchdowns. They were the only team in the regular season to keep the Rams under 20 points. They sacked Jared Goff three times and picked him off four times. Goff had a quarterback rating of 19 in the game with a completion percentage of 45%. Even if you eliminate the -81 quarterback rating differential from the Ram’s game, the Bears would still have the second best defensive quarterback rating differential. The Bears led the league in the number of games with 4+ defensive sacks with eight.
They did lose free safety Adrian Amos is free agency. However they picked up Ha Ha Clinton-Dix. In his five year career Clinton-Dix averaged three interceptions and six passes defended per 16 games. According to Pro Football Focus, Clinton-Dix has allowed a passer rating of just 52.9 on throws into his primary coverage since 2014, which is the best mark among all safeties in that time.
3. Buffalo Bills
The Bills were tie with the Ravens and the Bears for the lowest opponent yards per pass attempt with a 6.3 yards per attempt. Among genral NFL statistics, they were first in lowest opponent passing yards per game with 179.2 yards. The Bills were fourth in opponent 1st down passing percent with 31.9%. The Bills gave up the least amount of 20+ passing plays with 36 and also least of 40+ passing plays with 2. Opponent quarterbacks had the third lowest passer rating.
The Bills defense remained in tact thru free agency. They did pick up a pair of cornerbacks with E.J. Gaines and Kevin Johnson. Gaines made the NFL All-Rookie team in 2014 with 14 passes defended and two interceptions. His highest graded season from PFF was in 2017 when he got an 80.6 which was 17th among cornerbacks, Gaines was injured last year and played only six games for the Browns. Johnson was a first round pick in 2015. He has had an injury plagued career and only played in one game in 2018 and six in 2016. Before injury in 2016 Johnson was PFF’s seventh highest graded corner for the year.
In the 2019 draft the Bills selected defensive tackle Ed Oliver in round one. Oliver was All AAC First Team every year of his three college seasons. He was 2017 AAC Defensive Player of the Year and a Consensus All American in 2017 and 2018. Ed Oliver made #1 on Chase Goodbread’s NFL.com’s “18 for ’18: College football’s most freakish athletes” and #2 on Bruce Feldman’s 2018 college football Freaks List. He made my list of the five toughest draft prospects at each position. Oliver had 13.5 sacks over his 3 year college career and 32 games. His 5.5 sacks in 2017 was a 24% team market share which is just shy of a 25% indicative of future NFL success.
Bottom Three Teams 2018
30. Detroit Lions
The Lions had the second to last opponent quarterback rating differential (+172.6) and defensive quarterback hits (68). The league averages on those were -23 opponent quarterback rating and 88 defensive quarterback hits. The Lions had only four games where the opponent quarterback rating was below their team rating for the season. Only three players had double digit quarterback hits and none of them had more than 14.
Looking forwards the Lions signed defensive end Trey Flowers as a free agent from the Patriots. Flowers led the Patriots the last two years in quarterback hits with 20 in 2018 and 25 in 2017.
Strong safety Tracy Walker was chosen in round three of the 2018 draft. His rookie year he played in 27% of the defensive snaps or 267 snaps. He had one interception and two passes defended. Walker made Pro Football Focus’s 2018 Clutch Team Second Team. Their clutch team are the top players that played in at least 100 snaps during the fourth quarter of games that were within 7 points or less. Walker was the third highest graded NFL safety in that scenario. He was one of only three players on the Lions that earned a 75+ coverage grade from PFF.
31. Miami Dolphins
The Dolphins had the worst opponent passing yards per attempt differential at + 21.9 yards. The league average differential was + 9.7 yards. They had only four games where the opponent had a lower yards per attempt than their yearly average and those were all – 1.0 yards or a smaller negative yardage. They had two games of a +3 yards differential. Their worst was a 42 to 23 loss to the Texans in which Deshaun Watson had an 80% completion ratio, threw for 239 yards, five touchdowns and zero interceptions. The yards per passing attempt was 4.5 yards above their average.
Looking ahead to 2019 They lost defensive end Cameron Wake in free agency. Wake led the Dolphins in 2018 in quarterback hits and was second on the team in sacks. In 2017 he led the team in both sacks and hits and was fourth in the league in quarterback hits.
The Dolphins drafted defensive tackle Christian Wilkins with the 13th pick of the 2019 draft. Wilkins increased his sack count every year in college ending with 5.5 sacks his senior year. He was given a 91.0 pass rush grade for 2018 by Pro Football Focus which was fourth among defensive interior linemen and only 1.5 points below top rated Quinnen Williams. As reported by PFF he won 16.7% of his pass rushes which was third best among defensive interior linemen. His PFF pass rush grade jumped from 67.8 in 2017 to 91.0 in 2018. Also worth noting is Wilkins batted down 15 passes during his career.
32. Oakland Raiders
The Raiders ranked last in quarterback hits with only 48. The next lowest team, the Lions, had 20 more hits. Oakland was also last in the league in sacks with only 13. The next lowest team had 30. The Raiders were second to last in opponent passing yards per attempt differential with + 19.9 yards. They had worst game in the season for opponent yards per attempt differential with a + 7.4 yard differential against the Dolphins. In week three the Raiders lost 28 to 20 to Miami. The game had the second highest net passing yards per attempt of the season in the league with Ryan Tannehill passing for a net 13.28 yards per attempt.
The Raiders signed free agent safety LaMarcus Joyner in 2019. Though Joyner had a down year in 2018 the Raiders hope he repeats his 2017 season. That year he had three interceptions and nine passes defended in playing only 12 games. He received a 91.2 grade in coverage from Pro Football Focus which was third among all safeties. He has averaged six passes defended per 16 games over his five year career.
In the 2019 draft the Raiders picked defensive end Clelin Ferrell and safety Jonathan Abram in the first round. Ferrell had 11.5 sacks last year in college which was sixth in the FBS. Jonathan Abram had three sacks, two interceptions and five passes defended in his senior year. In round four of the 2019 draft they selected defensive end Maxx Crosby. In 2017 Crosby had 11 sacks which was good for sixth in the nation and a whopping 39% team market share of sacks. For each of the last two seasons Crosby has made the All-MAC First Team.
Three Most Improved Teams from 2017 to 2018
1. Cleveland Browns
In 2018 the Browns had a -158 opponent passer rating differential (5th), a -4.6 yards per attempt differential (8th) and 90 quarterback hits (15th). Their total 2018 ranking for pass defense was 8th. This was a dramatic increase from 2017 where they ranked 31st. That season they were last in passer rating differential with a + 219.7. In 2017 they had only three games where an opposing quarterback had a lower rating than his team’s season rating. Their worst game was a 31 to 7 loss to the Bengals in week 4. Bengals quarterback Andy Dalton had an 83% completion percentage and threw for 286 yards, four touchdowns and zero interceptions. Dalton had a 142.9 passer rating in the game which was the seventh best in the entire 2017 NFL season.
The Browns turnaround was helped by their 2018 first round pick safety Denzel Ward. In his rookie year Ward had three interceptions, 11 passes defensed, a forced fumble and two fumble recoveries. He made the 2018 NFL All-Rookie Team and was selected for the Pro Bowl. He was one of just three rookie defensive backs that had 10+ passes defensed and more than one interception.
The turnaround was also helped from improved play from their second year players. Their 2017 first round pick defensive end Myles Garrett practically doubled his rookie production. In 2018 Garrett had 29 quarterback hits, 13.5 sacks and three passes defended. He followed up a rookie year in which he made the All-Rookie Team with a trip to the 2018 Pro Bowl. Garrett was tie for fifth most quarterback hits in the league and had the sixth most sacks. He was one of only eight players that had 10+ sacks and 25+ quarterback hits.
Another second year player, defensive tackle Larry Ogunjobi, also had an outstanding year. After tripling his snap counts from 300 to 930 in 2018 Ogunjobi responded with 15 quarterback hits and 5.5 sacks. Those numbers were five times his 2017 statistics. Another 2018 rookie stepped up in a big way. Linebacker and fifth round 2018 draft pick Genard Avery had 14 quarterback hits and 4.5 sacks on 58% of the defensive snaps.
The Browns show no sign of letting up in 2019. They acquired defensive end Olivier Vernon in a 2019 trade and signed free agent defensive tackle Sheldon Richardson. Over his seven year career Vernon has averaged 20 quarterback hits and 8 sacks per 16 games. Looking over just the last three seasons those averages increase to 23 hits and nine sacks. This even though he has played injured over the last two seasons. Over his six year career Sheldon Richardson has averaged 4 sacks and 14 quarterback hits per 16 games. His last year in Minnesota he hit that average with 4.5 sacks and 16 quarterback hits.
In the 2019 draft some Browns’ defensive selections of interest are cornerback Greedy Williams in round two, linebacker Sione Takitaki in round three and cornerback Donnie Lewis in round seven. All three met market share targets indicative of success in the NFL. Williams had six interceptions in 2017 which was fourth in the FBS. Donnie Lewis leads all 2018 active FBS players in career passes defended with 49. His 21 passes defended in 2018 was fourth in the FBS.
2. New York Giants
In 2017 the Giants were tie with the Chiefs at 31st for defensive quarterback hits with 61. The league average was 88. They were 29th in defensive sacks with 27. Their overall defensive pass ranking here was 30th. In 2018 they have moved up to 18th.
In 2018 the Giants opponent passer rating differential was -111 for eighth best. Their 2017 differential was + 88.7 for 25th place. In 2017 they had five games with a 20+ passer rating differential and three of those were 44+ points. If you look at the top 17 games in 2018 by worst opponent passer differential the Giants are the only team on the list three times
Their 2017 opponent yards per attempt differential was +11 yards which ranked 26th. In 2018 it was +1.7 which was 18th. Their 2017 worst ranking in quarterback hits improved from 31st to 23rd with 81 hits. Their sacks increased to 30 but that fell in the ranking to 31st.
Defensive end Olivier Vernon had a Pro Bowl year with 21 quarterback hits and seven sacks in only 11 games. The 2018 trade for Alec Ogletree saw him lead the team in interceptions with five and he had the second most team passes defended (8). The 2018 free agent signing of safety Curtis Riley had Riley with a career high 5 passes defended and 4 interceptions. Rookie defensive end Lorenzo Carter contributed with 4 passes defended, 4 sacks and 10 quarterback hits on only 40% of the defensive snaps.
The 2019 season will see the results of losing safety Landon Collins in free agency and trading Olivier Vernon. The Giants had also traded defensive tackle Damon Harrison during the 2018 season. They signed safety Antoine Bethea as a free agent in 2019 . Bethea has averaged 3 interceptions and 7 passes defended per 16 games over the last two seasons. Also free agent linebacker Markus Golden was signed in 2019. Over his four year career Golden has averaged seven sacks and 15 quarterback hits per sixteen games.
In the 2019 draft the Giants loaded up on defensive players. They drafted three cornerbacks, two defensive tackles and two linebackers.
First round pick defensive tackle Dexter Lawrence was the heaviest player at the 2019 combine weighing in at 342 lbs. He had the second highest bench press reps of all players with 36. He is known for having a great work ethic. In his freshman year he recorded 6.5 sacks but that dropped to 2 and 1.5 his next two years. GM Dave Gettleman had this to say – “This kid can push the pocket and he can have an impact on the pass rush.”. Coach Pat Shurmur said – ” “Dexter, I was with (Vikings DT) Linval Joseph, who all of you know, in Minnesota and he sort of reminded me of him. He’s sneaky with the pass rush…”
In 2018 and 2017 first round pick cornerback Deandre Baker hit market share totals indicative of success in the NFL. He was a 2018 Consensus All American and the winner of the 2018 Jim Thorpe Award which is given to the most outstanding defensive back in college football. “The last guy we traded up for we feel is the best cover corner in the draft, the kid from Georgia, Deandre Baker.” – Dave Gettleman.
In the third round they picked defensive end Oshane Ximines. Ximines hit market share totals indicative of success in the NFL each of his last two seasons. Oshane Ximines had a 52.3% sacks market share. He averaged 1 sack per game which was fifth in the FBS. He is second among 2018 active FBS players in career sacks with 33.
3. Kansas City Chiefs
In 2017 the Chiefs were tied for 31st in defensive quarterback hits with 61. The league average was 88. They were tied at 25th in sacks with 31. The Chiefs were third to last in opponent passing yards per attempt differential with a + 15.4. They had four games with over a +2 yards per pass attempt differential including one with a +5.7 yards. There biggest improvement came in 2018 with quarterback hits. In 2018 they were fifth with 102. That is closing in on double what they had in 2017. They were tied for first in sacks in 2018 with 52.
In 2017 linebacker Dee Ford had a back injury flare up. It required surgery and there were concerns that he would be able to walk properly. He wound up playing only six games in 2017. Through perseverance and attention to his diet Ford was able to recover and played a full 16 games in 2018. He wound up having the best year of his five year career and was selected to the Pro Bowl. Ford ended the 2018 regular season with 29 quarterback hits, 13 sacks, seven forced fumbles and 77 pressures.
Defensive end Chris Jones watched the end of the 2017 season from the sidelines with an injury as the Chiefs lost to the Titans in the wild card rounds. He set a goal to make sure he had the fitness and the stamina to make himself a force in 2018. That is what he did. Jones had a career year in 2018 with 29 quarterback hits, 15.5 sacks, two forced fumbles, five passes defended and an interception. His 25.5 sacks was third in the league.
Together Jones and Ford made Kansas the only team to have two players in the top ten for both quarterback hits and sacks.
Among the defensive backs, cornerback Steven Nelson had a big year. He led the team in passes defensed (11) and interceptions (4). It was a career high for him. He was one of only three players with a combination of that many. In 2017 Nelson had missed half the season due to a preseason injury and core muscle surgery.
Going into 2019 the Chiefs lost some of their key contributors in free agency which included cornerback Stephen Nelson and linebacker Justin Houston, In his eight year career on the Chiefs Houston averaged 19 quarterback hits and 12 sacks per 16 games. His 2018 season saw 12 hits and 9 sacks.
They had some nice additions in free agency signing linebacker Jeremiah Attaochu, defensive end Alex Okafor and safety Tyrann Mathieu. Mathieu has averaged three interceptions and 10 passes defended per 16 games in his career. Pro Football Focus reports that Tyrann Mathieu is still yet to drop an interceptable pass. He is one of four safeties with at least 100 targets since 2014 to achieve this. Okafor has averaged 11 quarterback hits and 5 sacks per 16 games in his six year career. Last year he had 4 sacks and 9 hits. Attaochu has averaged 9 hits and 4 sacks per 16 games in his five year career. Last year he had 5 hits and 2 sacks in 11 games.
The Chiefs selected Safety Juan Thornhill in round two of the 2019 draft. Juan Thornhill had a 31.6% passes broken up market share with 12 from his 2017 season. Over the last two seasons Juan Thornhill has made the All-ACC team at safety (2018 First Team) and at cornerback (2017 Third Team). Thornhill came close to hitting market share thresholds of 6% solo tackle, 25% interception and 15% passes defended for each of the last three years. In 2016 and 2017 he made it but in 2018 missed only for passes defended with 11%. Among 2018 active FBS players Juan is tie for the most career interceptions with 13.
Three Most Declined Teams from 2017 to 2018
30. Cincinnati Bengals
In this ranking the Bengals dropped from 15th in 2017 to 26th in 2018. In 2018 the Bengals gave up the most passing yards with a 275.9 opponent passing yards per game. They gave up the third most passing plays of 20+ yards with 60.
The 2018 season saw the losses of some key players. After making the 2017 All-Rookie team in 2017, defensive end Carl Lawson tore his ACL in week 8 of the 2018 season and was out for the rest of the season. In 2017 Lawson was second on the team in quarterback hits (21) and sacks (8.5). Cornerback Adam Jones played in only 26% of the 2017 defensive snaps but according to Pro Football Focus through 13 weeks, he allowed just 15 receptions from 30 targets. He tallied one interception and four pass breakups, surrendering a passer rating of just 60.7 and an average of 0.81 yards per cover snap, which ranks 10th and 13th among 117 qualifying players at the position, respectively. Jones was placed on IR at the start of December 2017 and released in 2018. In 2017 defensive end Chris Smith played 35% of the defensive snaps and had 3 sacks and 9 quarterback hits. Smith was signed as a free agent by the Browns in March 2018.
In 2019 the Bengals released defensive tackle Adolphus Washington and signed free agent defensive end Kerry Wynn. Both had similar graded years by Pro Football Focus. In the 2019 draft the Bengals did not select a defensive player until linebacker Germaine Pratt in round three. Germaine Pratt was selected for the 2018 All-ACC First Team. Pratt played safety his first two seasons and has a career 4 interceptions and 9 passes defensed. His first season at linebacker as a junior Pratt had two interceptions with one returned for a touchdown. In addition Pratt had 22 total quarterback pressures in only 69 pass-rush snaps.
31. Seattle Seahawks
In this ranking the Seahawks were 7th in 2017 and fell to 19th in 2018. The once vaunted defense finished in the bottom half of the league in six out of ten NFL defensive passing statistics. There worst one was 24th place in giving up passing plays of 20+ yards with 58 for the season.
The 2018 season saw a loss of the longtime core defensive players on the Seahawks. In March of 2018 the Seahawks released cornerback Richard Sherman. They traded defensive tackle Sheldon Richardson during the draft. After suffering a season ending neck injury in week 10 of the 2017 season, Defensive back Kam Chancellor retired in July 2018. Defensive end Michael Bennett was traded to the Eagles in March 2018. The Seahawks also released defensive end Cliff Avril in May 2018.
In his seven years on the Seahawks Richard Sherman averaged 15 passes defended and 5 interceptions per 16 games. Before his injury in 2017 Kam Chancellor allowed just 12 catches on 25 targets as the primary coverage player. Only 28.0 percent of his targets had gone for first downs or touchdowns, and his coverage grade of 86.4 ranked 11th in the NFL among safeties, as reported by Pro Football Focus. In his one year on the Seahawks in 2017 defensive tackle Sheldon Richardson had 7 quarterback hits, one sack, a forced fumble and one interception. In his five years on the Seahawks Michael Bennett averaged 26 quarterback hits and eight sacks per 16 games. In his five years on the Seahawks Cliff Avril averaged 21 quarterback hits and eight sacks per 16 games.
In 2019 the exodus continues with safety Earl Thomas signing as a free agent with Baltimore. In his nine year career on the Seahawks Thomas averaged 9 passes defended and 4 interceptions per 16 games. According to Pro Football Focus among the 70 NFL safeties with at least 2,000 snaps played in the last five years, Thomas ranks first in overall grade (93.6) and coverage grade (97.2). Cornerback Justin Coleman signed as a free agent with the Lions. In his two seasons on the Seahawks Coleman averaged 2 interceptions and 10 passes defended per 16 games. According to Pro Football Focus he earned the fifth-highest slot coverage grade (81.8) and ranked seventh in first downs allowed per target (29.1%) . The Seahawks traded defensive end Frank Clark to the Chiefs for a first round draft pick. In 2018 Clark was the Seahawks leading player in quarterback hits (27) and sacks (13). In his four year career on the Seahawks, Clark averaged 19 quarterback hits and nine sacks per 16 games.
To help overcome the exodus the Seahawks did sign free agent defensive end Ezekiel Ansah in 2019. Ansah has averaged 22 quarterback hits and 10 sacks per 16 games over his six year career on the Lions.
In the 2019 draft the Seahawks picked up a pair of linebackers that are good in coverage. Ben-Burr Kirven was selected in the fifth round and Cody Barton in round three. In 2018 Kirven had an 18% interception team market share (2 interceptions) and an 11.5% passes defended team market share (6 passes defended). Those are good market share numbers for a linebacker. Pro Football Focus had Burr-Kirven ranked second behind LSU’s Devin White in coverage grade (91.2) in 2018. Cody Barton had a coverage grade of 86.6 at Utah last season, ranking 19th out of 518 qualifying linebackers. Barton had six passes defended and one interception in 2018. His passes defended team market share was 10% which was above average among linebackers that met a minimum 11.5% solo tackle team market share.
In round one they chose DE/DT L.J. Collier. Collier had 4+ sacks in each of his last three seasons finishing with 6 his senior year. In round four they selected cornerback Ugo Amadi . Amadi is slightly smaller than prototypical at 5’9″. He has had 6+ passes defended each of the last three seasons and 3+ interceptions each of the last two. Amadi was the winner of the 2018 Lombardi Award presented to a college football player, regardless of position, based on performance, as well as leadership, character, and resiliency. He was also one of 14 semi-finalists for the Jim Thorpe Award given to best defensive back in college football.
32. New Orleans Saints
The Saints were ranked 8th according to this exercise for 2017 and dropped to 21st in 2018. Their 2017 opponent passer rating differential was third at -198.7. It was a + 17.7 in 2018. They had six games in 2017 that had an opponent passer rating of -32 and worse. In 2018 they had zero games of -30 differential and only three with a -20 differential or worse. Their quarterback hits improved in 2018 and went from below average in 2017 to above average in 2018. The Saints were fifth in the league in sacks in 2018 with 49 sacks. In 2018 NFL statistics the Saints were in the bottom quarter of the league in opponent completion %, yards per attempt, yards per game, 1st down %, 40+ yard plays and passer rating.
In 2018 the Saints were tie with the Chiefs at 25th in the league in passes defended with 54. The league average was 65. They were tie with the Falcons and Seahawks at 31st in interceptions with seven. The league average was 13. There were only three teams that ranked that low in both statistics. They were Green Bay, Seattle and New Orleans.
The Saints had one of the youngest secondaries in 2018. Of their seven main players six had two or less years experience heading into the 2018 season. Three were 23 years old or less.
Going into 2019 the Saints released their one experienced player of the seven with the release of safety Kurt Coleman. The Saints had signed free agent Patrick Robinson in 2018 but he had broken his ankle in week three and was out for the season. In his prior three seasons after leaving the Saints as a free agent Robinson averaged 2 interceptions and 13 passes defended per 16 games.
In the 2019 draft the Saints picked a pair of safeties with Chauncey Gardner-Johnson in the fourth round and Saquan Hampton in the sixth. Gardner had 9 interceptions and 12 passes defended over his three years in college. In 2018 Saquan Hampton had great team market share numbers for his 44 solo tackles (10%), three interceptions (33%) and 13 passes defended (24.5%). Those team market share values are indicative of success in the NFL.
The data for all the teams can be downloaded here – pass defense. The data is sorted by decreasing change in rank from 2017 to 2018.