ปีก่อนปี 1980 ดัชนีเงินเฟ้อสูงสุดคือปีใด (2000=100)
What year before 1980 has is the highest Inflation Index (2000=100)?
df = pd.DataFrame(columns=['year', 'inflation_index__2000'])
df[(df['year'] < 1980) & (df['inflation_index__2000'] == 100)]['year'].values[0]