period,mean,sd,fracneg,tot,start_date,end_date
Ancestral,3.6723268091905314,3.6193177658133373,0.061330994598912836,230324,2020-01-01,2021-02-14
Alpha,3.576864677095167,3.2639690791690463,0.048686970200122345,183088,2021-02-15,2021-06-27
Delta,3.5819562886432643,3.0701055937022623,0.04410217354270425,99791,2021-06-28,2021-12-26
Omicron,3.4081596856802077,3.2274153528672445,0.04742861152038167,28506,2021-12-27,2022-04-11