Attack speed calculation?

I have +12% inc attack speed if holding a shield (from tree). I've done some testing while checking the Offece tab of the Default attack. The results:

Unarmed:
- 78% speed
- 90% speed with shield (12% increase)

Dagger with 1,45 attacks per second:
- 91% speed
- 103% speed with shield (12% increase)

Sword with 1,69 attacks per second:
- 131% speed
- 146% speed with shield (15% increase)

Why do I get 15% instead of 12%?

Do you have a talent with 3% attack speed with swords? Perhaps a jewel socketed in the passive tree that has it as a random stat you forgot about?

If you make your profile public so we can see your characters we might be able to help more.

Thanks for your reply!

I've double-checked these things and the "x% attack speed with swords" is already added when equipped the sword. The 15% difference is between sword+shield and sword+nothing which should be 12%. Maybe it's just a calculation error.

Anyway, gonna set my profile to public (character name: Csisy_ClawFlurry) but until then here is the current passive tree I'm using:
https://www.pathofexile.com/fullscreen-passive-skill-tree/AAAABAQDAQHcBIcFLQhJDY0UIBR1FewY2xutIWAj9igqKaUvzDIJMk41kjrhPeI9_ECgRrdHfkjuSn1NRk2STeNQR1boWGNbr18_YuxlTWxGcmx07XTxdqx343gNeK55aHrve9R82X11hJSE2YTvhVKHdolxivCLT4zPjX2PmZAKl3mbaqOKplepbq2NsbOy3LXyuR29Nr6nwBrAv8EEwYLEuMqQz37Tb9N-1fjYvdlh2sHdDeCV45_kUelG6hjsXO4O7w7yRfZI9zL8xf4K_o_-ug==?accountName=csisyadam&characterName=Csisy_ClawFlurry

Hi, are you sure, your attack speed is 131% with sword, because I check your profile, but i can't find way, how can you got 131%, in my test your attack speed with sword must be 133% or 134%

Items
10% from gloves

Tree nodes
10% from Unstoppable Hero (Fortify)
5% Strong Arm
8% (2x4%) Claw, Dagger and Sword Attack Speed
4% Weapon Artistry
10% (2x3% + 4%) Attack Speed
12% Art of the Gladiator
4% Born to Fight
8% Finesse
12% Berserking

Skill
42% Faster Attacks

Bandits
8% Kraityn
--------------------
133% attack speed

If you don't help Kraityn, then next option is buff from your Lightning Golem and in this case will be your attack speed 134% (9% from 17 lvl golem)

I'm checking the attack speed modifier of the default attack, so the Faster Attacks gem is irrelevant. Anyway, here are the screenshots:

Without shield:


With shield:


Edit:
Unequipped my whole gear and I have +68% attack speed modifier on the Default Attack (with Fority up, standing in my hideout). According to poeplanner.com I have:
- 10% attack speed while having Fortify
- 4% melee attack speed
- 46% attack speed
- 8% Kraityn
Total: 68% - this is good

After equipping my 1.69 aps sword the attack speed modifier goes up to +119%
- 10% while Fortify
- 4% melee
- 46% attack speed
- 5% with melee one handed
- 8% with swords
- 8% Kraityn
Total: 81% - 38% attack speed is "missing", it probably comes from the weapon's attack speed but I'm not sure how.

Anyway, equipping the shield gives me an extra +15% so the attack speed modifier of the Default Attacks became +134%. Adding the gloves (which should give +10%) the speed goes up to +146%.

This means that a magic number derived from the weapon's APS is multiplied by the total increases (so the 12% from shield became 15% and the 10% from gloves became 12%)

Edit 2:
A multiplier idea sounds right but here is the math:
78% unarmed (with full gear and fortify)

With swords: +5 +8 = 91%
Character panel shows 131%
91*x = 131
x = 131/91 = 1,4395604395604395604395604395604

Adding shield: +12 = 103
Character panel shows 146%
103*y = 146
y = 1,4174757281553398058252427184466

And the thing is that x != y

Thanks Vipermagi,

That's strange. The weapon attack speed is both multiplicative with the global attack speed and "post-additive" as well?

That gives the correct results:
With a sword only: 91% global * 1,21 + 21% local = 131,11 -> 131%
With a sword and shield: (91+12)% global * 1,21 + 21% local = 145,63 -> 146%

Edit:
After these calculations the weapon's original base attack speed is multiplied by the attack speed modifier, right? So the Harpy Rapier's base APS is 1,4 and the AS modifier is 146% so the final APS is 1,4 * (1 + 1,46) = 3,444 -> 3,45. That's why a higher base APS weapon will be faster.