Showing posts with label Fast bowling. Show all posts
Showing posts with label Fast bowling. Show all posts

Wednesday, 21 August 2013

When was the Ashes won?

The important old ball
England retained the Ashes by securing a draw in the 3rd match at Old Trafford, and then won the series by winning the 4th match at Chester-le-Street.

An interesting question, however, is what parts of the games did England win? It's hard not to recognise the efforts of Ian Bell, who has been immense for England with the bat, often on quite difficult surfaces. Despite his efforts, I think there has been another factor that has been equally influential. England's pace bowlers have bowled well with the old ball.

For the purpose of this article, I've defined the ball as being new if it is less than 20 overs old, and old if it's more than 20 overs.

Here are the difference between the two sets of pace bowlers:

AverageAustraliaEngland
less than 20 overs22.7832.32
more than 20 overs35.2828.78

Australia are significantly better with the new ball, but England are better with the old ball. While those 7 runs per wicket doesn't seem like a big difference, it is because there have been just over twice the number of overs bowled with the old ball as with the new ball.

Part of the difference has been that Australia seem to have worked hard to keep the shine on the ball, while England seem to have been trying to get the ball to reverse, and not been so worried about using the first new ball as a weapon. England have done much better with the second new ball than with the first (England average 4 runs per wicket more with the first new ball than with the second), while Australia have been the opposite (Australia average 5 runs per wicket more with the second new ball than with the first). Their bowlers almost seem to have run out of steam once the second ball comes along.

Here's how it works out as averages scores. After 20 overs Australia's average score is about 66/2. England is 58/3. However after 80 overs Australia average 180/9 while England are 225/7. Some of that difference is Graeme Swann, but some of that is just how much more effective England's quick bowlers have been with the older ball.

If we took spin bowlers out of the picture and just looked at the fast bowlers, After 20 overs Australia would still average 66/2 (Swann had been about as effective as the quicks with the new ball). England would have been 47/3. After 80 overs Australia would average 250/9 while England would still have 3 wickets in hand at 211/7.

There's a point, however, where these numbers are ridiculous, as the different batsmen are not equally capable, but they do paint a picture.

However they are ignoring the impact that Swann has on the bowlers that are bowling with him.

I believe that one of the reasons that England's quicks have been so effective with the old ball is the pressure created by Graeme Swann. To quantify this pressure, I looked at a statistic that I called Wicket Assists. A wicket assist is awarded to a bowler who bowls an over directly preceding the one where a wicket fell.

Wicket assists is a statistic that I keep note of when I'm coaching, as it's often a better indicator of how much pressure a bowler is exerting on the batsmen than wickets. An example of this is when I had two bowlers opening the bowling together. One bowled 6 overs, and took 0/8 (included 2 no balls, and a wide that just slipped down the leg side). The other bowled 7 overs and took 6/47. Most of the wickets for the second bowler were a result of the pressure that the first bowler built up. The second one got to keep the ball, and got the plaudits, however the one that I recommended for a higher team was the first bowler.

Graeme Swann has taken 23 wickets in this series, but he has also had 23 wicket assists. That's roughly one wicket every 9 overs while he's at the bowling crease. He creates pressure that allows the quick bowlers to take wickets. Compare his rate to Ashton Agar, who had 2 wickets and 5 assists in the two matches he played. That's a wicket roughly every 24 overs that he's at the crease. Nathan Lyon has been more successful than Agar at exerting pressure. 8 wickets and 6 assists, meaning that Australia pick up a wicket roughly every 11 overs that he's at the crease.

Overall I believe that one of the major differences between the two teams has been what their bowlers have done after 20 overs. England's quick bowlers have been better, and their spinners have been better too. Overall, I believe this is the time that this series has been won.

Thursday, 27 December 2012

A tale of two bowlers

I was chatting to someone yesterday, and mentioned that I thought Shaminda Eranga was the real deal. That we might be looking back and say "I saw him at the start of his career." Not long after I said that he was smacked at more than 6 an over by the Australian openers. Fortunately I had put a caveat when I was chatting. I said "but he's still not very good against left handers. He looks amazing against right handers."

He seems to get a little swing, but then seam movement away from the right handers. The small bit of swing means that the batsmen start to follow the ball with their hands, and then he takes the edge with the seam movement. He doesn't swing it enough that they play and leave, but rather just enough to draw them into the shot. (Most balls seem to only swing about 5 cm - it's the movement off the seam that makes him dangerous). However against the left handers this small swing means that if it's straight, they tend to defend it, and if it seams back, they just hit an inside edge into their pads.

So I thought I'd go through his (brief) career so far and see if my feeling is correct. Here are Shaminda Eranga's test statistics against right and left handed batsmen (prior to the Melbourne test):

HandAverageStrike RateEconomy Rate
Right24.0039.43.65
Left101.50195.03.12

There is a significant difference.

Of players who have bowled in at least 20 matches, the best strike rate ever is Sid Barnes, with 41.6. Next is Dale Steyn with 42.0 and the Waqar Younis with 43.4. Eranga to right handers has a better strike rate than any of these.

However the other end of the tail we see a bunch of part timers. With a strike rate in the region of 195 are the likes of Shivnarine Chanerpaul (193.3) and Geoff Howarth (204.6). Even Geoffrey Boycott had a bowling strike rate of 134.8. These are good people to be compared to if you are talking about defensive technique when batting, but not so much if you're talking about bowling.

If Eranga wants to make the most of his obvious talent, he will need to figure out how to bowl to lefties. He is a fantastic prospect for Sri Lanka, but they can't keep picking him if he's going to be two bowlers: Steyn to the right-handers but Boycott to the left handers.

Friday, 21 December 2012

Land of the long list of lefties

In a few hours New Zealand will take the field against South Africa. There are two players likely to be named in the team who's selection will be quite remarkable.

Corey Anderson is a big all rounder from Canterbury (originally) who hits a big ball and bowls left-arm medium fast. He was a prodigious talent at youth level, making the Canterbury side at age 16, while still at school.

Mitchell McClenaghan is a left-arm fast bowler who is a little erratic and injury prone, but who has a tendency to take wickets. Lots of wickets. Think of him as a New Zealand version of Mitchell Johnson. Not always on target, but capable of occasionally bowling a ball that could get through Rahul Dravid or Brian Lara.

While their selections are not in themselves particularly notable, there is one thing that is: they are both left-arm pace bowlers, adding to a very long list of NZ left-armers.

This year New Zealand has used Trent Boult, Niel Wagner, Andy McKay, James Franklin and Michael Bates at the bowling crease. There is only one other year in history when a team has selected 5 left-arm pace bowlers to play international cricket. In 2007 Sri Lanka actually picked 6 (although Zoysa didn't actually bowl in the one match he was selected for).

And New Zealand are probably against the best team to bowl left-arm pace against. South Africa's batsmen have done well against every type of bowling, but they have done less well against left-arm pace than any other type. In the last 4 years they average about 41 against right arm spin, 39 against left-arm spin or right arm pace but only 35 against left-arm pace. An average of 35 suggest that left-arm pace isn't a silver bullet, but it is a significant difference, and one that New Zealand might be aware of.

So far this year most of the South African batsmen have been dismissed at least once by a left-armer, despite many of them having only faced a couple of innings from a left-armer. Here are the stats for everyone who has faced a left-arm pace bowler at least 5 times:

NameTotal RunsTotal DismissalsAverage
Smith1221122
A Petersen66416.5
Amla162281
Kallis100425
de Villiers1421142
Levi34217
Duminy210-
du Plessis96196

The New Zealand bowlers are likely to be eagerly waiting to bowl to Petersen and Kallis. The battle between the South African batsmen and the New Zealand left-armers is certainly one aspect of the tour that I'm going to be looking forward to watching immensely.

Thursday, 13 December 2012

Is Dale Steyn the best bowler ever?

I recently read a (typically) good piece by Ant Sims about Dale Steyn. Some of the numbers that she came up with were very impressive. It got me wondering. Is Dale Steyn the best bowler ever?

She had the idea to compare him to other bowlers at a similar stage in their career. I decided to do something similar, so I looked at a large number of bowlers who had bowled in either 60 matches or 100 innings to look at how they compared at that point of their career.

Some players tend to hold on for a long time after their peak. Sometimes it is because everyone (including them) thinks that they are just one innings away from recapturing their glory days (think Ricky Ponting), or because they are still one of the best from their nation, even though they are no longer nearly as good as they were (think Sir Frank Worrell). But for what ever reason, about 60 games is often when a lot of bowlers reach their statistical zenith. They are experienced enough to know how to take wickets, but not old enough that they have lost too much energy.

Probably the most important statistic for bowlers in test matches is the average. Once I had pulled out all the bowlers data, there was one extraordinary number in the list: 20.14 by Shaun Pollock. Steyn is in the middle of this list.


The next thing that I look at is strike rate. Steyn is a strike bowler. It is not his job to hold up one end. He is there to take wickets. Strike rate is a measure of how many deliveries it takes a bowler on average to take a wicket. Generally the best bowlers tend to take wickets slightly better than every 10 overs, giving a strike rate under 60.

Here Steyn really shines. He has the second best strike rate of any bowler after 60 matches. And then he's only marginally behind Waqar Younis. Here's another way to put it. The first two bowlers I remember vividly from when I grew up were Malcolm Marshall and Richard Hadlee. Steyn is more likely to get a wicket on any given ball than either of them were.

Another measure is bowling index. This is a more complicated statistic, which is described in the glossary. While it is best suited for comparing bowlers in limited overs matches, it does tell a story in tests also. It really tells us who has kept the batsmen honest while they have been taking their wickets. It's not perfect, but it is interesting. (You may need to scroll to see Steyn's numbers in this one)


Again we see Shaun Pollock on top, and by a reasonable margin, this time ahead of Deadly Derek Underwood. Steyn is near the bottom of the list, along with the majority of the bowlers in the era of boundary ropes and uncompressed bats.

So to answer the question: is Dale Steyn the best bowler ever? Probably not, that's possibly Shaun Pollock, but Steyn is certainly up there with the best.

For a different way of looking at the greatest bowlers ever, and to see where Steyn is placed on that list, you can also try this article that I wrote at the beginning of the year. The numbers need updating, but they were right as at the 7th of January.

Sunday, 22 April 2012

India's quick men in the IPL

One of the real bonuses for India with having the IPL is it provides an opportunity for their 2nd tier bowlers and batsmen to test their skills against the best in the world.

With a few notable exceptions, India have not had a reputation for producing quality fast bowling. In some ways the IPL is the perfect vehicle for this to change. With foreign coaches coming in, and high quality seamers in every team there is no excuse for Indian players to not develop their games.

So it's interesting to see who has taken advantage of this. Who is getting better, and who is stagnating? And which bowlers are consistently providing world class performances?

Firstly I looked at the Average and Economy Rate for the last 10 IPL matches for the 11 best performing Indian quick bowlers who had bowled in at least 4 matches this IPL. Here are the numbers:

PlayerAverageE/r
M Patel11.56.72
R Bhatia20.256.19
A Dinda19.387.64
Zaheer Khan23.757.13
U Yadav25.257.77
L Balaji25.567.8
A Nehra24.678.22
A Singh26.258.55
S Trivedi27.788.15
R Vinnay Kumar34.678.67
P Kumar85.336.92

There's a mixed bag there. Some (like Ashish Nehra and Ashok Dinda) have been good at taking wickets, but have gone for a lot of runs. Others (like Zaheer Khan and particularly Praveen Kumar) have been economical, but have not taken many wickets.

There can be arguments about which is the most important, but ideally a bowler will have a good economy rate and a good average. I feel that a quality player should average under 25 and have an economy rate of under 7.5.

The graph shows 3 players making the grade (Patel, Bhatia, Zaheer), and one just missing out (Dinda). One player actually doesn't even fit on the graph at all: Praveen Kumar. However, he is so far below the economy rate line that he is worth considering.

So once I had isolated the best performers of the Indian quick bowlers, the next question was to look at each of them in detail, to see if they had been making the most of the opportunities that had been afforded to them through the IPL.

Munaf Patel

Munaf Patel has really been the stand out of the Indian quick bowlers. He has taken wickets, but without conceding many runs. And the chart shows that his numbers are getting better and better. It's difficult to change a career economy rate in 4 overs, but almost every game the career rate is decreasing. The rate of improvement suggests that there is still more to come from him also.

Munaf Patel is shaping up as a bowler who could in the future genuinely look the likes of Malinga, Steyn and Broad in the eye. 10 wickets for 89 runs this IPL suggests that he possibly already can.


Zaheer Khan

Zaheer has been a steady performer for a while now. He's become very consistent, partially because batsmen know the danger they are in when he is bowling, and so take less risks. He still takes a wicket roughly every 3 overs.

He does not seem to have got much benefit from the IPL, but he was already a top bowler before the competition really got established.

Rajat Bhatia

This name was new to me. There have not been many KKR matches on at times that are friendly for someone in my time-zone to watch, and his results never really stood out on the score sheets.

We can see that his results (particularly his economy rate) have been steadily improving. Combine this with some useful lower-order hitting in some non-IPL t20 matches (including 107* off 60 for Delhi against Railways), Bhatia looks like a very useful performer.

Unfortunately he's 32, and the Indian selectors are much more likely to look at youth, than try out a player who only offers a few years service. This is a pity, as his numbers are very impressive (if you were to take his figures and Zaheer Khan's figures and compare them, on all but 19 of the 177 days that they have been in season Bhatia has had a better average, and in all but 21 he's had a better economy rate)

Ashok Dinda

Ashok Dinda has done very well this season. He's taken his career average down from the mid 30's to the mid 20's and maintained an economy rate around 7 runs per over.

He's managed to upstage his more illustrious colleagues Ashish Nehra, Angelo Mathews and Wayne Parnell, and in the process really establish himself as a very reliable contributor. He's gone at less than 6 an over so far this season, and if he keeps that up, an international recall may be on the cards.

The graph clearly shows what is sometimes called 2nd year syndrome. A player has a good start, so everyone tries to figure out how to play them. The test of a great player is if they can come back from this and have a great third year. It seems to have taken a little longer than that for Dinda, but this year (his 5th in the IPL) is shaping up to be his best yet.

Praveen Kumar

Despite Praveen Kumar's average skyrocketing during the last 10 or so matches, he has continued to make it difficult for the batsmen to score.

This whole article stemmed out of me researching to decide who to pick in my fantasy team, and despite what the numbers suggest, I actually went for Praveen Kumar. The reason is that it seems unlikely to me that a bowler can keep putting batsmen under pressure, and for that to continue to not result in wickets. Eventually someone is going to target him, and he'll either go for a lot of runs, or pick up their wicket. The interesting thing in this graph is the demonstration of how his game has changed. From a bowler who in one 10 match period averaged 20's but went for close to 8 an over, to a player who now averages a lot higher, but goes for less runs per over.

Sometimes a bowler like that causes so much pressure that a wicket falls at the other end. Peter Siddle is a good example of a bowler who also does that. The bowler at the other end bowls a bad ball and it gets hit down a fielders throat.

If I were an Indian selector, I would certainly take heart from the start of the IPL. Bhatia has to be coming into reckoning, as does Dinda, and once Varun Arron and RP Singh are back from injury, there could be a real surplus of talented quick bowlers for them to chose from. This is not a position that India has historically enjoyed very often.

*all statistics are accurate before the start of play on 21/4/2012

Thursday, 23 February 2012

The great choke

I've just gotten home from watching New Zealand lose an unlosable match to South Africa at Eden Park.

It was a terrible match to watch as a New Zealand fan, but a fascinating game as a cricket purist. Here were 5 things I noticed:

1. Jesse Ryder found then lost his mojo.

Ryder came out and started off well. He was scoring quite quickly, but he was (generally) doing it in sensible ways, and (finally) was moving his feet like he did in 2010, rather than standing and swishing like he did against Australia earlier this year.

Then the rain came. And he lost his foot work and his batting sense. With 5 overs to go, Ryder was on 44 off 25. He had been scoring well with boundaries, but off the 20 balls that he didn't hit to the fence he had scored 16. From his next 16 balls he scored 8 runs. He was pre-determining, not moving his feet and was generally like a possum in headlights, or Sachin Tendulkar right before a break.

2. Kane Williamson suddenly stopped being Kane Williamson.

If Williamson was a superhero his name would be Placement Boy. He has the ability to find the gaps and put the ball where he wants it to be. And that ability completely evaded him. Instead he hit 6 of 8 before going for a mad heave across the line rather than trying to hit a single.

3. Franklin and McCullum not swapping ends.

New Zealand needed 6 off 4, and nMac tried a paddle scoop shot. While it's a bit unorthodox, there's nothing particularly wrong with that. What was disappointing was the batsmen not crossing while the ball went half way to the moon before getting into de Villiers' gloves.

Franklin jogged through, rather than running through. McCullum stood and watched in horror as the ball headed to the keeper, and hardly moved at all. It was a play that a second division business house team would have been distraught at. It mean that the new man needed to face the next ball, and was somehow expected to score immediately, rather than leaving it up to the batsman who was in. Poor, poor cricket.

4. Sending out Southee rather than Hira to bat for the last ball.

Southee is a good bowler. He can hit a big ball. But it is a stretch to accuse him of having a track record of heady cricket. Hira is known precisely for playing smart cricket.

While it was likely that the batsman who was sent out would not need to face a ball, there was always the chance that there would be a no ball, and having someone who was quick to make a good decision would be a good idea. Someone who could get back for a second would be hugely valuable.

But instead New Zealand sent out Southee instead of the Worlds Fastest Indian. Having someone who could get (even halfway) back would have left Franklin in strike needing 3 or 4 to win, and potentially 2 to tie, and Hira there to run like only Hira or Guptill can.

5. Four bouncers in an over.

Marchant de Lange managed to find the zone just between where a batsman finds it comfortable to play a short ball and where an umpire will start to warn him for it.

His final over contained 4 bouncers, and he was still allowed his 1 per over, as none of them were high enough in the opinion of the square leg umpire to be his 1 for the over.

Conventional wisdom suggests that the best option at the death is full and straight, but at Eden Park, with the new layout of short straight boundaries and longish square ones full and straight is asking for trouble. Instead he bowled a fantastic final over and put all the pressure back on the New Zealand batsmen.

It seems in the age of darting left arm spinners, that there is still a place for aggressive fast bowling.

Monday, 23 January 2012

Big Occasion Bates

Yesterday the (mighty) Auckland Aces were playing in their third consecutive HRV Cup final. Auckland won convincingly. During the time between their first and third final they have also played Pakistan in a tour T20 match and played 2 Champions League matches.

Throughout these 6 big occasion matches one player has really been extraordinary: left arm quick bowler Michael Bates.

Here are his results:
MatchOppositionResultFigures
2009/10 HRV Cup finalCentral DistrictsLoss4-0-61-3
Tour matchPakistanWin3-0-11-4
2010/11 HRV Cup FinalCentral DistrictsWin4-1-18-4
2011 Champions League T20Kolkata Knight RidersLoss4-0-13-1
2011 Champions League T20SomersetLoss4-1-13-2
2011/12 HRV Cup FinalCanterburyWin3-0-18-3
Overall 22-2-134-17

This gives him an average of 7.88, an economy rate of 6.09 and a strike rate of 7.64. If we just look at the last 2 years, removing the first final at the postage stamp sized Pukekura Park, his figures become 18-2-73-14. That is a breath-takingly low economy rate of 4.06, average of 5.2 and strike rate of 7.71.

How good are those numbers? Here are some comparisons: The best averaging bowler in the world is Krishmar Santoki from Jamaica who averages 8.56; the best economy rate is Samuel Badree from Trinidad and Tobago who's economy rate is 4.43; the best strike rate is also Santoki at 9.3. Bates's figures in the last 5 finals are better than all of these. Now it is true that 5 matches is a small sample size, but the results are still outstanding.

Given these numbers it is staggering that he hasn't been picked up by an overseas team of some variety. He hasn't even been picked for New Zealand A.

Now sometimes a bowler can get good figures by getting bad batsmen out. Not the case with Bates, here is the list of his dismissals:
Ross Taylor*
Kieran Noema-Barnett
Jacob Oram*
Mohammad Hafeez*
Shahid Afridi*
Ahmed Shezad*
Wahab Riaz
Peter Ingram*
Jamie How*
Ian Blackwell*
Doug Bracewell
Manvinder Bisla
Peter Trego
Nick Compton
Rob Nichol*
Andrew Ellis
Reece Young*
* - has batted in the top 6 in International Cricket

In his other T20 matches, when the stage is not so big, he has preformed reasonably well, but not nearly as well as he has on the big stage. Here are his stats excluding these matches: 86.5-1-755-25 Average 30.2, Economy Rate 8.73, Strike Rate 20.76.

Teams need consistent performers. But they also need players that can step up on the big occasions. So far Michael Bates has proved that he can do just that.

Tuesday, 27 December 2011

Two unusual stumpings.

This post is a little more anorackish and a little less statistical than my usual posts.

I was enjoying the ability to watch two games at the same time today. I was flicking between the 2nd day of the Australia India test, and the HRV Cup twenty20 match between Central Districts and Wellington.

Wellington were demonstrating their ability to find a way to lose from what looked like a certain winning position, which was making me quite happy, as I had put some money on CD to win. During the game I noticed two interesting dismissals.

Stumping One Cachopa st van Wyk b Nethula

First it was Tarun Nethula who bowled a very effective spell of 1/16 off 4 overs. He bowled a delivery that seemed to drift in quite sharply to an advancing Craig Cachopa. It came off the inside edge, and started rolling towards the crease. Quick as a flash Kruger van Wyk was around the stumps, picked up the ball and took off the bails.

My understanding of the law was that the keeper was not allowed to take the ball in front of the stumps for a stumping. So I assumed that the dismissal would have to be changed to a run out. One of the commentators on TV (Mark Richardson) felt the same.

However I went to my trusty copy of Tom Smith's New Umpiring and Scoring to see what it had to say about this situation. It took a bit of reading, but it turns out that the dismissal was in fact correct and was stumped. The key passage is in law 40 (The Wicket-keeper) section 3:

"The wicket-keeper shall remain wholly behind the wicket at the striker’s end from the moment the ball comes into play until (a) a ball delivered by the bowler either (i) touches the bat or person of the striker or (ii) passes the wicket at the striker’s end or (b) the striker attempts a run."

Clearly once the ball hits the batsman or bat, it is fair game, and van Wyk was completely right to come out from behind the stumps and go for the ball.

Stumping Two Boam st van Wyk b Milne

Harry Boam Wellington's last hope was facing New Zealand's fastest bowler, Adam Milne. Well, he wasn't really Wellington's last hope - the match was long gone, but it sounds more dramatic to imagine that there was something on it. Wellington needed 26 runs off the last 2 deliveries, with the batting powerhouse that is Muttiah Muralitheran at the other end. I've once seen Andre Adams win a game off the last delivery when 11 were needed, but 26 off 2 is a little ridiculous. Still he was on 47 and within sight of a pyrrhic 50. So he came down the pitch and tried to hoist Adam Milne into the Wellington harbour.

This plan would have been more effective if he had made contact with the ball. Instead he got himself tide up in knots and lost all sense of balance and direction. the ball carried through unimpinged to van Wyk who was standing about 20 meters behind the stumps. Van Wyk was alert to the situation and, still gloved, threw down the stumps, leaving Boam short of his ground by about 2 meters. Not only was this a sensational piece of work to throw down the stumps with a glove still on, it created an interesting situation. Was it run out or stumped.

We generally don't think of a stumping off a fast bowler. (To be fair we don't often think of any sort of dismissal off a fast bowler in New Zealand - we are the nation that invented dibbly-dobbly bowling, where 130km/h is considered express pace) Normally that is the domain of spin bowlers or occasionally medium pacers. However the rules do not define who is allowed to take a stumping.

In fact the rules are very clear that if a batsman is not attempting a run, is out of his ground and the ball is "kicked or thrown onto the stumps by the wicket-keeper" then it is to be considered a stumping. Which meant that it was disappointing when the scorers on TV described the dismissal as "Boam run out (van Wyk)."

Fortunately the umpires afterwards communicated with the scorers and Adam Milne got given credit for what is likely to be his only ever stumping in his career (provided he doesn't replicate Shane Thompson and go from being a 150km/h quick bowler to an innocuous spinner - with a nasty bouncer).

I have umpired in two games this year when an opening batsman (same in both matches) was stumped by a keeper standing back to a quick bowler (same bowler-keeper combination both times, once in a 1-day game, once in a 2 day game), but both of these were a case of the batsman taking guard outside his crease, and not being aware enough to step back into his ground. (once is understandable, the second time incurred the wrath of his captain, and he batted at 9 for the second innings). The difference between these two situations is that the games I was umpiring were involving 15 year-old's and not professional cricketers, and both time it wasn't good bowling that drew the batsman out, and got him tangled up, it was just poor awareness.

Kruger van Wyk you have earned yourself the title of Cricketgeek hero of the week, and a like on Facebook.