The 'Law of total tricks'

High level bidding
When both camps have irregular fitted hands, the bidding can be competitive until high levels.
If a camp has shown at least 23H or committed to going to game without bidding it, iit is said to be in " offense", the opps camp is then in "defense". Examples of NS camps NS in 'offense' :
South West North

S	O	N	E

S	O	N	E

S	O	N	E

In these cases,

Either North South plays a contract it is hoping to make,
or East West plays a sacrificecontract it thinks will go down... but hopes to not go down too much or not be doubled

As a consequense,

Pass, by a player in offense is forcing and encourages his partner to overbid
The double is punitive and discourages his partner from overbidding

"Pass" and "double" by the camp on offense
In these cases,

Either North South plays a contract it is hoping to make,
or East West plays a sacrificecontract it thinks will go down... but hopes to not go down too much or not be doubled

As a consequense,

Pass, by a player in offense is forcing and encourages his partner to overbid
The double is punitive and discourages his partner from overbidding

With a reasonable doubt, you should overbid : on the one hand, the opps could get it wrong by overbidding as well, on the other hand it avooids big swings when both games make. It's a sort of insurance.

S	W	N	E

Exercise E20652 In South overbid to 5 ♦ with this hand : You'll avoid a catastrophy if 4♥ doubled makes and 5♦ also makes..

Decision support : Should you overbid ?

Your distribution is the key criteria in the decision to overbid. Consequently a hand rich in HCP and defensive tricks should prioritize doubling
The 'Law of total tricks' : When both camps have approximatively the same points count , The number of tricks to split between the 2 camps is equal to the sum of the number of cards help by each camp in its long suit.
lower honors, mainly Jacks and Queens, do not have the same value in attack and in defense
- They have a lot more value in offense in a long suit
- They have no value in defense in a short suit
Vulnerabilities play a large part in decision making : Down tricks, doubled and vulnerable can be very costly