shall decrease
Regular verb: decrease - decreased- decreased

Affirmation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I'll decrease
you'll decrease
she'll decrease
we'll decrease
you'll decrease
they'll decrease 	I'll be decreasing
you'll be decreasing
she'll be decreasing
we'll be decreasing
you'll be decreasing
they'll be decreasing	I'll have decreased
you'll have decreased
she'll have decreased
we'll have decreased
you'll have decreased
they'll have decreased	I'll have been decreasing
you'll have been decreasing
she'll have been decreasing
we'll have been decreasing
you'll have been decreasing
they'll have been decreasing	

Negation 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
I shan't decrease
you shan't decrease
she shan't decrease
we shan't decrease
you shan't decrease
they shan't decrease 	I shan't be decreasing
you shan't be decreasing
she shan't be decreasing
we shan't be decreasing
you shan't be decreasing
they shan't be decreasing	I shan't have decreased
you shan't have decreased
she shan't have decreased
we shan't have decreased
you shan't have decreased
they shan't have decreased	I shan't have been decreasing
you shan't have been decreasing
she shan't have been decreasing
we shan't have been decreasing
you shan't have been decreasing
they shan't have been decreasing	

Interrogative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
shall I decrease?
shall you decrease?
shall she decrease?
shall we decrease?
shall you decrease?
shall they decrease? 	shall I be decreasing?
shall you be decreasing?
shall she be decreasing?
shall we be decreasing?
shall you be decreasing?
shall they be decreasing? 	shall I have decreased?
shall you have decreased?
shall she have decreased?
shall we have decreased?
shall you have decreased?
shall they have decreased? 	shall I have been decreasing?
shall you have been decreasing?
shall she have been decreasing?
shall we have been decreasing?
shall you have been decreasing?
shall they have been decreasing? 	

Interro-negative form 	
Simple form 	V-ing form 	Perfect 	V-ing perfect 	
shan't I decrease?
shan't you decrease?
shan't she decrease?
shan't we decrease?
shan't you decrease?
shan't they decrease? 	shan't I be decreasing?
shan't you be decreasing?
shan't she be decreasing?
shan't we be decreasing?
shan't you be decreasing?
shan't they be decreasing? 	shan't I have decreased?
shan't you have decreased?
shan't she have decreased?
shan't we have decreased?
shan't you have decreased?
shan't they have decreased? 	shan't I have been decreasing?
shan't you have been decreasing?
shan't she have been decreasing?
shan't we have been decreasing?
shan't you have been decreasing?
shan't they have been decreasing?