It irritates me no end when experts talk about a side needing 20 wickets to win a test. At the risk of sounding pedantic, I'm going to point out that there have been 131 tests in which a team lost despite losing less than 20 wickets. Ofcourse most of the teams that lost in such a manner did so because one or more of their batsmen were either retired hurt or absent hurt.
However, there have been numerous instances in which a team has declared either or both its innings and gone on to lose. South Africa lost at the SCG in 2006 because Graeme Smith was ready to risk losing the series 2-0 if it gave him a chance to level it at 1-1. He declared both innings and Australia chased down the target on the back of a second hundred in the game from captain Ricky Ponting. Less than a year later Shane Warne masterminded the collapse that broke England's spirit for the remainder of the series. Warne and his mates had looked insipid in the first innings when England piled on a score of 551/6 before declaring their innings. India's historic win at Chennai came after Kevin Pietersen had declared England's second innings with one wicket remaining.
Sure these occurrences are rare (Statsguru doesn't allow me to sort the declared innings from the others), but they do happen. More often than a team winning despite scoring less runs than the opposition. How many times has a team done that? Never. Why? Because in test cricket, just like in any other sport, you cannot win if you don't score more than the opposition. And yet experts keep talking about how bowlers win you matches, how you're not a world class side if you don't have a strong bowling attack, how you can't win if your bowlers don't have the ability to take 20 wickets.
Saying you need 20 wickets to win a test is the biggest cliche in cricket. You can say it because it's not like you can take more than 20 wickets. But can anyone predict the number of runs to win a test before the start of the match? Obviously not, because in order to win you need atleast one more run than the opposition although you could win by scoring a lot more as well. On the other hand, you could score a lot more runs than the opposition and yet not win! So while scoring more than the opposition is a necessary condition to win a test, it may not be sufficient. But taking 20 wickets is neither a necessary nor a sufficient condition to win.
If you took a snap poll among cricketers on who has the better bowling attack between India and Pakistan the verdict would be overwhelmingly in favour of the latter. A similar poll on the batting strength of the two sides would result in India getting the vote over their neighbours. And yet it's the Indian team that hasn't lost a series in two years (They have won 5 during this period, 4 if you exclude Bangladesh), while Pakistan have lost two series and not won any during the same period.
The only two teams both have faced during this period are Sri Lanka (Home and Away) and New Zealand (Away). India beat Sri Lanka at home while Pakistan drew against Sri Lanka (The first test was drawn and the second one was cut short after the attack on the Sri Lankan team bus). Pakistan lost to Sri Lanka 2-0 away from home, failing to chase a sub-200 target in one of the tests while India drew their series in Sri Lanka 1-1, chasing down a 200-plus target in the final test. Coming to New Zealand, India beat the Kiwis 1-0 and it might well have been 2-0 had it not rained on Day 5 with India needing just two more wickets. Pakistan, on the other hand, drew their series 1-1. You can say Bond didn't play against India and New Zealand won the only test he played against Pakistan, but Pakistan would have lost had it not rained on Day 5 of the final test at Napier.
This isn't an exercise in proving India is better than Pakistan when it comes to test cricket. I've used these two teams because they have forever played contrasting styles of cricket. A few years ago Pakistan were clearly the better test side because they had batsmen like Saeed Anwar, Javed Miandad, Salim Malik, Inzamam-ul-Haq to go along with bowlers like Wasim, Waqar, Imran, Shoaib, Saqlain. Compare that lineup to the current lineup that has only one batsman averaging over 40 and you know why Pakistan aren't among the top sides in the world. In contrast, India have figured out ways to win in all conditions with Zaheer Khan being the only consistent performer. Each of their top 4 averages over 50 and the number 5 batsman averages almost 60 over the last 4 years, while the captain averages over 60 when he's leading the side.
The two greatest test sides were so good because they were extremely strong in both disciplines. It's not like Marshall, Holding, Garner and Roberts had a bunch of bunnies batting in their side. Greenidge, Haynes, Richards, Lloyd is as strong a top four as you'll get. The Australian juggernaut had Hayden, Langer, Ponting, Waughs, and Gilchrist. They have combined for over 150 test hundreds!
The point I'm making is there are different ways to be a quality test side. While being a strong batting side doesn't guarantee it, being a great bowling side doesn't either. Remember, you can't win unless you score more than the opposition but you can win even if you take less wickets than them.
Edit: David Barry just showed me how to filter out finished innings so that we only have innings which were declared.