TTT, what do you mean by contributing? Do you mean only tax payers should vote, if so, do you mean income tax? How would that work? Would folk need to have worked for a set number of weeks within a past period to qualify?
What about those who pay no income tax but pay VAT? They contribute virtually every time they buy messages or use various services. How would it be monitored?
There are thousands of volunteers who carry out any number of activities which contribute toward society without making a payment. Would they be barred?