[Fort Denton]

I have an AMEX Gold Delta Skymiles Card with a limit of $2000. I pay the card off religiously. I recently received notice that my limit was being decreased from 2000 to 1500. I had just recently paid the full balance of 1300off and had a balance of 0. I called AMEX and the man said that my average spending on the card was $1300 per month and that was the reason for the lowering of the limit. He said that after reviewing my account (I have had the card for only 6 months), AMEX had determined that my spending was too high ($1300). But I pay it off in full most months and had just paid it off as I mentioned earlier. I was hoping that someone here could help me understand why I am considered "not as good of a credit risk" as I was 6 months ago when I pay the card off almost every month. Is it because I do pay it off too much and AMEX doesnt make enough interest off of my account? Can someone help me understand because the AMEX customer service rep really did not tell me anymore than what I have just written here.

Thanks in advance for any help