A general rule of thumb is that if your economic model has no value judgements, it's positive economics, and if it does have value judgements it's normative economics, since to tell someone what he ought to do, you first have to judge what is best for him.
A subscriber identity module or subscriber identification module (SIM) is an integrated circuit that is intended to securely store the international mobile subscriber identity (IMSI) number and its related key, which are used to identify and authenticate subscribers on mobile telephony devices (such as mobile phones and computers).
The SIM card is a memory circuit in your cell phone that carries necessary information back and forth to your network, and it also contains some of your personal data. While the information that your service provider needs is not changeable or removable, you can control some aspects of your personal information.ne way you can protect your SIM card in case of loss or theft is to contact your service provider and ask them to lock the SIM card. This simple step prevents anyone from reading your SIM card or using it in another phone. Keep in mind that this step does not lock your phone.