These numbers are from all WotC Published materials
25% of level 1 Wizard Spells have Concentration
60% of level 2 Wizard Spells have Concentration
52% of level 3 Wizard Spells have Concentration
65% of level 4 Wizard Spells have Concentration
60% of level 5 Wizard Spells have Concentration
51% of level 6 Wizard Spells have Concentration
20% of level 7 Wizard Spells have Concentration
40% of level 8 Wizard Spells have Concentration
40% of level 9 Wizard Spells have Concentration
Worth noting the two following important pieces of information:
1) Where you see Concentration Spells jump ahead of non-concentration spells really hard are the levels where you have 3-5 spells that do the exact same thing with a different flavor. Like the "Investiture of (Element)" spells or "Summon Aberration/Construct/Elemental/Demon"
2) You can still -cast- a spell which requires Concentration while you have Strife. You just can't -maintain- that concentration across multiple rounds.
So even if you've got Strife you can conjure up a Bigby's Hand and immediately command it to push the Ogre off the cliff. You just can't -keep- the Bigby's Hand the next turn.
25% of level 1 Wizard Spells have Concentration
60% of level 2 Wizard Spells have Concentration
52% of level 3 Wizard Spells have Concentration
65% of level 4 Wizard Spells have Concentration
60% of level 5 Wizard Spells have Concentration
51% of level 6 Wizard Spells have Concentration
20% of level 7 Wizard Spells have Concentration
40% of level 8 Wizard Spells have Concentration
40% of level 9 Wizard Spells have Concentration
Worth noting the two following important pieces of information:
1) Where you see Concentration Spells jump ahead of non-concentration spells really hard are the levels where you have 3-5 spells that do the exact same thing with a different flavor. Like the "Investiture of (Element)" spells or "Summon Aberration/Construct/Elemental/Demon"
2) You can still -cast- a spell which requires Concentration while you have Strife. You just can't -maintain- that concentration across multiple rounds.
So even if you've got Strife you can conjure up a Bigby's Hand and immediately command it to push the Ogre off the cliff. You just can't -keep- the Bigby's Hand the next turn.