Pure sector Allocation

Does it assume that within each sector, the manager held exactly same underlyings as the benchmark?

That is the way I understand it since it is comparing the weight of the investors portfoilo to the weight of the benchmark portfolio allocated to that sector and multiplying by the benchmarks return in that sector minus total portfolio return.

Pure sector allocation does not consider the return that the investment portfolio earned in that sector, therefore it assums the manager held the same underlyings as the benchmark.

I would like someone elses input on this as well.

Thanks both.