运行N次都是出错（得数出错），帮忙找下错误

#include <stdio.h>
int main(void)
{
int year = 10;
float rate = 0.08;
float sum = 100;
int i = 0;
while(sum < year)
{ sum = sum * rate;
sum = sum - year;
i++;
}
printf("需要%d年chuckie就会清空他的账户\n", i);
return 0;
}
找不出- - 晕倒