The gross earnings of the association shall be ascertained annually, and there shall first be deducted therefrom the expenses incurred by the association for the preceding year and the balance thereof shall be set aside as a reserve fund for the payment of contingent losses, to an amount equal to two percent (2%) of the capital stock outstanding, and until such reserve fund equals twenty percent (20%) of the capital stock of such association. (1925, c. 223, s. 23.)