Why is my propensity score match equal to 1?

[candicetait]

Hello, 

I ran a psmatch procedure to match companies by size and roa in the same industry class (Fama-French 28) and it returned some matches with a propensity score of exactly 1. 

I don't know why this has happened, can you help? 

My code below: 

proc psmatch data=m9 region=treated;
class treat ff48;
psmodel treat (treated="1")= size ff48;
match distance=lps method=Greedy(k=1) exact=ff48 caliper=0.5;
assess lps var=(size roa)/ weight=none plots=(boxplot barchart);
output out(obs=match)=OutEx4_&y matchid=_MatchID;
run;

Thank you in advance,

Candice

Propensity Scores propensity score matching code 

[Haris]

Propensity score of 1 means that the probability of the target treatment is 100% for a company based on your model and the values of the covariates.