list index out of range при попытке записи чисел из одного списка в другой

Много раз пытался записать конкретные элементы из двумерного списка в другой список. Всякий раз получал list index out of range.

import csv

mas = []
y_val = []
with open ('24_Чита.csv', 'r', newline = '') as csvfile:
    spreader = csv.reader(csvfile, delimiter = ',')
    for row in spreader:
        mas.append((list(row)))
print(mas)                

# все работает хорошо до этого цикла
for i in range(1, 13):
    y_val.append(mas[i][1]) # здесь и появляется ошибка выхода за пределы массива

print(y_val)

Ниже привел некоторое содержимое mas.

[['Year,"January","February","March","April","May","June","July","August","September","October‚","November","December","Srednyaa"'], ['1890,"999.9","999.9","999.9","999.9","999.9","15.6","19.3","15.3","8.9","1.4","-15.2","-27.4","999.9"'], ['1891,"-27.7","-21.7","-9.8","-1.8","8","14.3","19.8","16.4","7.2","-2.8","-18.8","-26.9","-3.7"'], ['1892,"-31.6","-26.6","-17.3","-1.6","7.7","15.7","17.3","14.9","7.7","-0.8","-15.6","-23.6","-4.5"']...