안녕하세요. rolling regression 이라는 것을 파이썬으로 하고 있는데,a,b,c, r2의 숫자가 변하지 않습니다. 뭐가 잘못된 걸까요?

import matplotlib.pyplot as plt
import statsmodels.api as sm
import statsmodels.formula.api as sm1


start = 0
end = 60
timeseries = {"period":[],
              "A": [], 
              "B":[],
              "C":[],
              "R2":[]} 


while end <= len(d):
    df = d.iloc[start:end]
    period = str(df.index[0].to_timestamp().to_period('M')) + " to " + str(df.index[-1].to_timestamp().to_period('M'))
    model= sm1.ols(formula = 'Q("KS11") ~ Q("000001.SS") +Q("GSPC") ',data= d).fit()
    model_result = model.summary()

    x = df['000001.SS','GSPC']
    y = df['KS11']
    x = sm.add_constant(x)
    model = sm.OLS(y,x).fit()
    model_result = model.summary()


    timeseries["period"].append(period)
    timeseries["R2"].append(model.rsquared)
    results_as_html = model_result.tables[1].as_html()
    timeseries["A"].append(pd.read_html(results_as_html, header=0, index_col=0)[0]["coef"][0]) 
    timeseries["B"].append(pd.read_html(results_as_html, header=0, index_col=0)[0]["coef"][1]) 
    timeseries["C"].append(pd.read_html(results_as_html, header=0, index_col=0)[0]["coef"][2]) 
    start+=1  
    end+=1

timeseries_result = pd.DataFrame.from_dict(timeseries)