Error binding parameter 0 - probably unsupported type.

[illmattic]

Hoping I can get some help on this error:

c.execute("INSERT INTO USMoneySupply (MonetaryBase, M1, M2) VALUES (?, ?, ?)", sqlite3.InterfaceError: Error binding parameter 0 - probably unsupported type.

api_key = open('quandlapikey.txt', 'r').read()

def data_extract(code):
    data = quandl.get(code, authtoken=api_key, collapse='monthly')
    data['Y/Y, (%)'] = data['Value'].pct_change(12)*100
    return data

m2 = data_extract('FRED/M2')
m1 = data_extract('FRED/M1')
mb = data_extract('FRED/BOGMBASEW')

conn = sqlite3.connect('Database.db')
c = conn.cursor()

def create_table():
    c.execute("CREATE TABLE IF NOT EXISTS USMoneySupply(MonetaryBase REAL, MonetaryBasePer REAL, M1 REAL, M1Per REAL, M2 REAL, M2Per REAL)")

def data_entry():
    mb_data = mb['Value']
    mb_per = mb['Y/Y, (%)']
    m1_data = m1['Value']
    m1_per = m1['Y/Y, (%)']
    m2_data = m2['Value']
    m2_per = m2['Y/Y, (%)']
    c.execute("INSERT INTO USMoneySupply (MonetaryBase, MonetaryBasePER, M1, M1Per, M2, M2Per) VALUES (?, ?, ?, ?, ?, ?)",
              (mb_data, mb_per, m1_data, m1_per, m2_data, m2_per))
    conn.commit()

create_table()
data_entry()
c.close()
conn.close()

Thank you.