The Company regularly updates its reserve estimates as new information becomes available and further events occur which may impact the resolution of unsettled claims. Reserve adjustments are reflected in results of operations as adjustments to losses and loss adjustment expenses (“LAE”). Often these adjustments are recognized in periods subsequent to the period in which the underlying policy was written and loss event occurred. These types of subsequent adjustments are described as “prior years’ loss reserves.” Such development can be either favorable or unfavorable to the Company’s financial results and may vary by line of business. In this section, all amounts presented include catastrophe losses and LAE, unless otherwise indicated.

The table below provides a reconciliation of the gross beginning and ending reserve for unpaid losses and loss adjustment expenses.

	Nine Months Ended
	September 30,
(in millions)	2021			2020
Gross reserve for losses and LAE, beginning of period	$	6,024.0		$	5,654.4
Reinsurance recoverable on unpaid losses		1,641.6			1,574.8
Net reserve for losses and LAE, beginning of period		4,382.4			4,079.6
Net incurred losses and LAE in respect of losses occurring in:
Current year		2,427.1			2,176.0
Prior years		(56.7	)		(26.1	)
Total incurred losses and LAE		2,370.4			2,149.9
Net payments of losses and LAE in respect of losses occurring in:
Current year		981.0			863.5
Prior years		1,036.5			1,028.7
Total payments		2,017.5			1,892.2
Net reserve for losses and LAE, end of period		4,735.3			4,337.3
Reinsurance recoverable on unpaid losses		1,804.8			1,608.4
Gross reserve for losses and LAE, end of period	$	6,540.1		$	5,945.7

As a result of continuing trends in the Company’s business, reserves, including catastrophes, have been re-estimated for all prior accident years and were decreased by $56.7 million and $26.1 million in 2021 and 2020, respectively.

For the nine months ended September 30, 2021, net favorable loss and LAE development was $56.7 million, primarily as a result of net favorable Commercial Lines development of $34.6 million and favorable Personal Lines development of $23.1 million. Commercial Lines favorable development was primarily due to lower than expected losses of $13.1 million within the workers’ compensation line, primarily in accident years 2014 through 2019, and to lower than expected catastrophe losses of $12.0 million for hurricanes, tornadoes, and other storms in accident years 2018 through 2020. Personal Lines favorable development was primarily due to lower than expected losses of $20.1 million in the personal automobile line, driven by lower personal injury protection and bodily injury losses primarily in accident year 2020.

For the nine months ended September 30, 2020, net favorable loss and LAE development was $26.1 million primarily as a result of net favorable Commercial Lines development of $30.9 million, partially offset by unfavorable development in the Other Segment. Commercial Lines favorable development was primarily due to lower than expected losses of $25.6 million within the workers’ compensation line in accident years 2016 through 2019 and, within other commercial lines, $15.3 million within the marine line primarily in accident years 2017 through 2019, partially offset by higher than expected losses of $10.6 million in the commercial automobile line driven by higher personal injury protection and bodily injury losses, primarily in accident years 2017 through 2019. In addition, Other Segment unfavorable development was due to the Company’s run-off voluntary assumed property and casualty reinsurance pools business primarily based on an updated third-party actuarial study received in the first quarter of 2020 for the legacy Excess and Casualty Reinsurance Association (“ECRA”) pool that primarily consists of asbestos and environmental exposures.