Solve accuracy of exponential averaging

I wil forecast amount of applicant for next year in an university using exponential averaging, but it can not work anyone know? there is 13 time series data, i would predict in 14th data

person = [12947 11617 9107 8050 6402 5771 5321 5207 4512 4626 4675 4125 4926];
person_table = [1:13; person];
p = 0.7;

hold off;

plot ([1:13],person,'k');
hold on;


for x = [2:1:14]
   out1(x) = p * person(x - 1) + (1 - p) * out1(x - 1)
end

% plot the results in dotted lines
plot ([1:14], out1,'r:');

% graph labels
title('Number of student registrants every year');
xlabel('Year');
ylabel('Person');

% MAD and MSE calculations
error2 = person - out1(1:13);
expo2_MAD = sum(abs(error2))/13
expo2_MSE = sum(error2 .* error2)/13