There shall be maintained at all times assets in cash or securities authorized by the laws of the state in which the principal office of the attorney is located for the investment of similar funds of insurance companies doing the same kind of business in^* an amount equal to fifty percent of the net annual advance premiums or deposits collected and credited to the accounts of subscribers on policies having one year or less to run and pro rata on those for longer periods; or, in lieu thereof, one hundred percent of the net unearned premiums or deposits collected and credited to the accounts of subscribers, which assets shall not be charged as a liability.