Number of Players @ the table

Does the number of players at the table affect the effectiveness of card counting? I am a newbie to the message board and card counting. Therefore, I have been dealing myself simulated games with chips and everything @ my kitchen table. When I have played just myself and the dealer, I have been wearing it out, but whenever I deal multiple players I am getting worn out. It seems that if I start with a favorable count by the time it gets to the dealer, the count has turned unfavorable. Any comments?