What was the percentage change in the average repurchase price per share between 2017 and 2018?
{"Amount paid to repurchase shares": {"2019": "$  \u2014", "2018": 95125.0, "2017": 29993.0}, "Number of shares repurchased": {"2019": "\u2014", "2018": 1696.0, "2017": 422.0}, "Average repurchase price per share": {"2019": "$  \u2014", "2018": 56.07, "2017": 71.07}}
avg_repurchase_price_2018 = df["Average repurchase price per share"]["2018"]
avg_repurchase_price_2017 = df["Average repurchase price per share"]["2017"]
answer = (avg_repurchase_price_2018 - avg_repurchase_price_2017) / avg_repurchase_price_2017 * 100.0